diff --git a/app/packager_main.cc b/app/packager_main.cc
index 5f80965262..865541ecec 100644
--- a/app/packager_main.cc
+++ b/app/packager_main.cc
@@ -36,9 +36,9 @@ const char kUsage[] =
 namespace media {
 
 void DumpStreamInfo(const std::vector<MediaStream*>& streams) {
-  printf("Found %d stream(s).\n", streams.size());
+  printf("Found %zu stream(s).\n", streams.size());
   for (size_t i = 0; i < streams.size(); ++i)
-    printf("Stream [%d] %s\n", i, streams[i]->info()->ToString().c_str());
+    printf("Stream [%zu] %s\n", i, streams[i]->info()->ToString().c_str());
 }
 
 // Create and initialize encryptor source.
diff --git a/media/base/aes_encryptor.cc b/media/base/aes_encryptor.cc
index 367c96e726..9ab61c2fee 100644
--- a/media/base/aes_encryptor.cc
+++ b/media/base/aes_encryptor.cc
@@ -109,7 +109,7 @@ void AesCtrEncryptor::UpdateIv() {
     counter_ = iv_;
     counter_.resize(AES_BLOCK_SIZE, 0);
   } else {
-    DCHECK_EQ(16, iv_.size());
+    DCHECK_EQ(16u, iv_.size());
     // Even though the block counter portion of the counter (bytes 8 to 15) is
     // treated as a 64-bit number, it is recommended that the initialization
     // vector is treated as a 128-bit number when calculating the next
diff --git a/media/base/buffer_writer_unittest.cc b/media/base/buffer_writer_unittest.cc
index 7d0f0d1087..0aacd83f38 100644
--- a/media/base/buffer_writer_unittest.cc
+++ b/media/base/buffer_writer_unittest.cc
@@ -98,7 +98,7 @@ TEST_F(BufferWriterTest, AppendNBytes) {
 TEST_F(BufferWriterTest, AppendEmptyVector) {
   std::vector<uint8> v;
   writer_->AppendVector(v);
-  ASSERT_EQ(0, writer_->Size());
+  ASSERT_EQ(0u, writer_->Size());
 }
 
 TEST_F(BufferWriterTest, AppendVector) {
@@ -157,7 +157,7 @@ TEST_F(BufferWriterTest, Clear) {
   writer_->AppendInt(kuint32);
   ASSERT_EQ(sizeof(kuint32), writer_->Size());
   writer_->Clear();
-  ASSERT_EQ(0, writer_->Size());
+  ASSERT_EQ(0u, writer_->Size());
 }
 
 TEST_F(BufferWriterTest, WriteToFile) {
@@ -170,15 +170,16 @@ TEST_F(BufferWriterTest, WriteToFile) {
   writer_->AppendArray(kuint8Array, sizeof(kuint8Array));
   ASSERT_EQ(sizeof(kuint8Array), writer_->Size());
   ASSERT_OK(writer_->WriteToFile(output_file));
-  ASSERT_EQ(0, writer_->Size());
+  ASSERT_EQ(0u, writer_->Size());
   ASSERT_TRUE(output_file->Close());
 
   // Read the file and verify.
   File* const input_file = File::Open(path.value().c_str(), "r");
   ASSERT_TRUE(input_file != NULL);
   std::vector<uint8> data_read(sizeof(kuint8Array), 0);
-  EXPECT_EQ(sizeof(kuint8Array),
-            input_file->Read(&data_read[0], data_read.size()));
+  EXPECT_EQ(
+      sizeof(kuint8Array),
+      static_cast<size_t>(input_file->Read(&data_read[0], data_read.size())));
   ASSERT_TRUE(input_file->Close());
 
   for (size_t i = 0; i < sizeof(kuint8Array); ++i)
diff --git a/media/base/demuxer.cc b/media/base/demuxer.cc
index 7c1523c540..ed19cf2e79 100644
--- a/media/base/demuxer.cc
+++ b/media/base/demuxer.cc
@@ -17,7 +17,7 @@
 #include "media/mp4/mp4_media_parser.h"
 
 namespace {
-const int kBufSize = 0x40000;  // 256KB.
+const size_t kBufSize = 0x40000;  // 256KB.
 }
 
 namespace media {
diff --git a/media/base/fake_prng.cc b/media/base/fake_prng.cc
index 74ef19e5b4..6b86c6e8db 100644
--- a/media/base/fake_prng.cc
+++ b/media/base/fake_prng.cc
@@ -23,7 +23,7 @@ int FakeBytes(uint8* buf, int num) {
   DCHECK(buf);
   DCHECK(g_rand_source_fp);
 
-  if (fread(buf, 1, num, g_rand_source_fp) < num) {
+  if (fread(buf, 1, num, g_rand_source_fp) < static_cast<size_t>(num)) {
     LOG(ERROR) << "Ran out of fake PRNG data";
     return 0;
   }
diff --git a/media/base/http_fetcher_unittest.cc b/media/base/http_fetcher_unittest.cc
index aaf1ed2269..d2b9e46529 100644
--- a/media/base/http_fetcher_unittest.cc
+++ b/media/base/http_fetcher_unittest.cc
@@ -12,7 +12,6 @@
 #include "media/base/status_test_util.h"
 
 namespace {
-const int kHttpOK = 200;
 const int kHttpNotFound = 404;
 
 const char kTestUrl[] = "http://packager-test.appspot.com/http_test";
diff --git a/media/base/media_base.gyp b/media/base/media_base.gyp
index 946b77d986..1af7470254 100644
--- a/media/base/media_base.gyp
+++ b/media/base/media_base.gyp
@@ -5,6 +5,10 @@
 # https://developers.google.com/open-source/licenses/bsd
 
 {
+  'variables': {
+    # Compile as chromium code to enable warnings and warnings-as-errors.
+    'chromium_code': 1,
+  },
   'target_defaults': {
     'include_dirs': [
       '../..',
diff --git a/media/base/media_stream.cc b/media/base/media_stream.cc
index 6af62dcf53..c9d2f6c5f1 100644
--- a/media/base/media_stream.cc
+++ b/media/base/media_stream.cc
@@ -80,7 +80,7 @@ Status MediaStream::Start(MediaStreamOperation operation) {
       } else {
         // We need to disconnect all its peer streams which are not connected
         // to a muxer.
-        for (int i = 0; i < demuxer_->streams().size(); ++i) {
+        for (size_t i = 0; i < demuxer_->streams().size(); ++i) {
           Status status = demuxer_->streams()[i]->Start(operation);
           if (!status.ok())
             return status;
diff --git a/media/base/stream_info.cc b/media/base/stream_info.cc
index f14fda23ae..387e510ca0 100644
--- a/media/base/stream_info.cc
+++ b/media/base/stream_info.cc
@@ -36,7 +36,7 @@ StreamInfo::~StreamInfo() {}
 
 std::string StreamInfo::ToString() const {
   return base::StringPrintf(
-      "type: %s\n codec_string: %s\n time_scale: %d\n duration: %d "
+      "type: %s\n codec_string: %s\n time_scale: %d\n duration: %lu "
       "(%.1f seconds)\n language: %s\n is_encrypted: %s\n",
       (stream_type_ == kStreamAudio ? "Audio" : "Video"),
       codec_string_.c_str(),
diff --git a/media/base/stream_info.h b/media/base/stream_info.h
index bb2652824c..d92cd18a55 100644
--- a/media/base/stream_info.h
+++ b/media/base/stream_info.h
@@ -39,7 +39,7 @@ class StreamInfo : public base::RefCountedThreadSafe<StreamInfo> {
   virtual std::string ToString() const;
 
   StreamType stream_type() const { return stream_type_; }
-  int track_id() const { return track_id_; }
+  uint32 track_id() const { return track_id_; }
   uint32 time_scale() const { return time_scale_; }
   uint64 duration() const { return duration_; }
   const std::string& codec_string() const { return codec_string_; }
@@ -58,7 +58,7 @@ class StreamInfo : public base::RefCountedThreadSafe<StreamInfo> {
  private:
   // Whether the stream is Audio or Video.
   StreamType stream_type_;
-  int track_id_;
+  uint32 track_id_;
   // The actual time is calculated as time / time_scale_ in seconds.
   uint32 time_scale_;
   // Duration base on time_scale.
diff --git a/media/base/widevine_encryptor_source.cc b/media/base/widevine_encryptor_source.cc
index 16e9d12331..3f43cde920 100644
--- a/media/base/widevine_encryptor_source.cc
+++ b/media/base/widevine_encryptor_source.cc
@@ -72,7 +72,7 @@ bool GetPssh(const base::DictionaryValue& track_dict,
   RCHECK(track_dict.GetList("pssh", &pssh_list));
   // Invariant check. We don't want to crash in release mode if possible.
   // The following code handles it gracefully if GetSize() does not return 1.
-  DCHECK_EQ(1, pssh_list->GetSize());
+  DCHECK_EQ(1u, pssh_list->GetSize());
 
   const base::DictionaryValue* pssh_dict;
   RCHECK(pssh_list->GetDictionary(0, &pssh_dict));
diff --git a/media/event/media_event.gyp b/media/event/media_event.gyp
index cbd033f1ec..d52b8513cf 100644
--- a/media/event/media_event.gyp
+++ b/media/event/media_event.gyp
@@ -5,6 +5,10 @@
 # https://developers.google.com/open-source/licenses/bsd
 
 {
+  'variables': {
+    # Compile as chromium code to enable warnings and warnings-as-errors.
+    'chromium_code': 1,
+  },
   'target_defaults': {
     'include_dirs': [
       '../..',
diff --git a/media/event/muxer_listener.h b/media/event/muxer_listener.h
index 7cf4e80466..dc4fa75b41 100644
--- a/media/event/muxer_listener.h
+++ b/media/event/muxer_listener.h
@@ -15,8 +15,8 @@
 
 namespace media {
 
-class MuxerOptions;
 class StreamInfo;
+struct MuxerOptions;
 
 namespace event {
 
diff --git a/media/event/vod_media_info_dump_muxer_listener.cc b/media/event/vod_media_info_dump_muxer_listener.cc
index fa11eb8c83..11b0be4bae 100644
--- a/media/event/vod_media_info_dump_muxer_listener.cc
+++ b/media/event/vod_media_info_dump_muxer_listener.cc
@@ -24,16 +24,6 @@ namespace {
 const char kEncryptedMp4Uri[] = "urn:mpeg:dash:mp4protection:2011";
 const char kEncryptedMp4Value[] = "cenc";
 
-bool IsAnyStreamEncrypted(const std::vector<StreamInfo*>& stream_infos) {
-  typedef std::vector<StreamInfo*>::const_iterator Iterator;
-  for (Iterator it = stream_infos.begin(); it != stream_infos.end(); ++it) {
-    if ((*it)->is_encrypted())
-      return true;
-  }
-
-  return false;
-}
-
 // |user_scheme_id_uri| is the user specified schemeIdUri for ContentProtection.
 // This adds a default ContentProtection element if the container is MP4.
 // Returns true if a ContentProtectionXml is added to |media_info|, otherwise
diff --git a/media/event/vod_muxer_listener_internal.cc b/media/event/vod_muxer_listener_internal.cc
index 1e6b4b3f4e..d2fd3e4807 100644
--- a/media/event/vod_muxer_listener_internal.cc
+++ b/media/event/vod_muxer_listener_internal.cc
@@ -88,7 +88,7 @@ void SetMediaInfoCommonInfo(float duration_seconds,
                             MuxerListener::ContainerType container_type,
                             MediaInfo* media_info) {
   DCHECK(media_info);
-  DCHECK_GT(file_size, 0);
+  DCHECK_GT(file_size, 0u);
   DCHECK_GT(duration_seconds, 0.0f);
 
   media_info->set_media_duration_seconds(duration_seconds);
diff --git a/media/event/vod_muxer_listener_internal.h b/media/event/vod_muxer_listener_internal.h
index 5f4c03dd91..6f8ee6d731 100644
--- a/media/event/vod_muxer_listener_internal.h
+++ b/media/event/vod_muxer_listener_internal.h
@@ -18,8 +18,8 @@ class MediaInfo;
 
 namespace media {
 
-class MuxerOptions;
 class StreamInfo;
+struct MuxerOptions;
 
 namespace event {
 namespace internal {
diff --git a/media/file/file.gyp b/media/file/file.gyp
index 36014f7dd3..c4ddbf46aa 100644
--- a/media/file/file.gyp
+++ b/media/file/file.gyp
@@ -5,6 +5,10 @@
 # https://developers.google.com/open-source/licenses/bsd
 
 {
+  'variables': {
+    # Compile as chromium code to enable warnings and warnings-as-errors.
+    'chromium_code': 1,
+  },
   'target_defaults': {
     'include_dirs': [
       '../..',
diff --git a/media/mp4/aac_audio_specific_config.cc b/media/mp4/aac_audio_specific_config.cc
index 640f566402..a7f02f2c24 100644
--- a/media/mp4/aac_audio_specific_config.cc
+++ b/media/mp4/aac_audio_specific_config.cc
@@ -138,7 +138,7 @@ uint32 AACAudioSpecificConfig::GetOutputSamplesPerSecond(bool sbr_in_mimetype)
   // The following code is written according to ISO 14496 Part 3 Table 1.11 and
   // Table 1.22. (Table 1.11 refers to the capping to 48000, Table 1.22 refers
   // to SBR doubling the AAC sample rate.)
-  DCHECK_GT(frequency_, 0);
+  DCHECK_GT(frequency_, 0u);
   return std::min(2 * frequency_, 48000u);
 }
 
diff --git a/media/mp4/aac_audio_specific_config_unittest.cc b/media/mp4/aac_audio_specific_config_unittest.cc
index 2da1c486b0..9dc87b13ed 100644
--- a/media/mp4/aac_audio_specific_config_unittest.cc
+++ b/media/mp4/aac_audio_specific_config_unittest.cc
@@ -17,8 +17,8 @@ TEST(AACAudioSpecificConfigTest, BasicProfileTest) {
   data.assign(buffer, buffer + sizeof(buffer));
 
   EXPECT_TRUE(aac_audio_specific_config.Parse(data));
-  EXPECT_EQ(aac_audio_specific_config.GetOutputSamplesPerSecond(false), 44100);
-  EXPECT_EQ(aac_audio_specific_config.GetNumChannels(false), 2);
+  EXPECT_EQ(44100u, aac_audio_specific_config.GetOutputSamplesPerSecond(false));
+  EXPECT_EQ(2u, aac_audio_specific_config.GetNumChannels(false));
 }
 
 TEST(AACAudioSpecificConfigTest, ExtensionTest) {
@@ -29,9 +29,9 @@ TEST(AACAudioSpecificConfigTest, ExtensionTest) {
   data.assign(buffer, buffer + sizeof(buffer));
 
   EXPECT_TRUE(aac_audio_specific_config.Parse(data));
-  EXPECT_EQ(aac_audio_specific_config.GetOutputSamplesPerSecond(false), 48000);
-  EXPECT_EQ(aac_audio_specific_config.GetOutputSamplesPerSecond(true), 48000);
-  EXPECT_EQ(aac_audio_specific_config.GetNumChannels(false), 2);
+  EXPECT_EQ(48000u, aac_audio_specific_config.GetOutputSamplesPerSecond(false));
+  EXPECT_EQ(48000u, aac_audio_specific_config.GetOutputSamplesPerSecond(true));
+  EXPECT_EQ(2u, aac_audio_specific_config.GetNumChannels(false));
 }
 
 // Test implicit SBR with mono channel config.
@@ -48,12 +48,12 @@ TEST(AACAudioSpecificConfigTest, ImplicitSBR_ChannelConfig0) {
   EXPECT_TRUE(aac_audio_specific_config.Parse(data));
 
   // Test w/o implict SBR.
-  EXPECT_EQ(aac_audio_specific_config.GetOutputSamplesPerSecond(false), 24000);
-  EXPECT_EQ(aac_audio_specific_config.GetNumChannels(false), 1);
+  EXPECT_EQ(24000u, aac_audio_specific_config.GetOutputSamplesPerSecond(false));
+  EXPECT_EQ(1u, aac_audio_specific_config.GetNumChannels(false));
 
   // Test implicit SBR.
-  EXPECT_EQ(aac_audio_specific_config.GetOutputSamplesPerSecond(true), 48000);
-  EXPECT_EQ(aac_audio_specific_config.GetNumChannels(true), 2);
+  EXPECT_EQ(48000u, aac_audio_specific_config.GetOutputSamplesPerSecond(true));
+  EXPECT_EQ(2u, aac_audio_specific_config.GetNumChannels(true));
 }
 
 // Tests implicit SBR with a stereo channel config.
@@ -67,12 +67,12 @@ TEST(AACAudioSpecificConfigTest, ImplicitSBR_ChannelConfig1) {
   EXPECT_TRUE(aac_audio_specific_config.Parse(data));
 
   // Test w/o implict SBR.
-  EXPECT_EQ(aac_audio_specific_config.GetOutputSamplesPerSecond(false), 24000);
-  EXPECT_EQ(aac_audio_specific_config.GetNumChannels(false), 2);
+  EXPECT_EQ(24000u, aac_audio_specific_config.GetOutputSamplesPerSecond(false));
+  EXPECT_EQ(2u, aac_audio_specific_config.GetNumChannels(false));
 
   // Test implicit SBR.
-  EXPECT_EQ(aac_audio_specific_config.GetOutputSamplesPerSecond(true), 48000);
-  EXPECT_EQ(aac_audio_specific_config.GetNumChannels(true), 2);
+  EXPECT_EQ(48000u, aac_audio_specific_config.GetOutputSamplesPerSecond(true));
+  EXPECT_EQ(2u, aac_audio_specific_config.GetNumChannels(true));
 }
 
 TEST(AACAudioSpecificConfigTest, SixChannelTest) {
@@ -83,8 +83,8 @@ TEST(AACAudioSpecificConfigTest, SixChannelTest) {
   data.assign(buffer, buffer + sizeof(buffer));
 
   EXPECT_TRUE(aac_audio_specific_config.Parse(data));
-  EXPECT_EQ(aac_audio_specific_config.GetOutputSamplesPerSecond(false), 48000);
-  EXPECT_EQ(aac_audio_specific_config.GetNumChannels(false), 6);
+  EXPECT_EQ(48000u, aac_audio_specific_config.GetOutputSamplesPerSecond(false));
+  EXPECT_EQ(6u, aac_audio_specific_config.GetNumChannels(false));
 }
 
 TEST(AACAudioSpecificConfigTest, DataTooShortTest) {
diff --git a/media/mp4/box_buffer.h b/media/mp4/box_buffer.h
index 6056f919a4..9a054ce830 100644
--- a/media/mp4/box_buffer.h
+++ b/media/mp4/box_buffer.h
@@ -144,7 +144,7 @@ class BoxBuffer {
     if (reader_)
       return reader_->ReadChild(box);
     // The box is mandatory, i.e. the box size should not be 0.
-    DCHECK_NE(0, box->atom_size);
+    DCHECK_NE(0u, box->atom_size);
     CHECK(box->ReadWrite(this));
     return true;
   }
diff --git a/media/mp4/box_definitions.cc b/media/mp4/box_definitions.cc
index a8e1b7cd5e..d69d6ae9fa 100644
--- a/media/mp4/box_definitions.cc
+++ b/media/mp4/box_definitions.cc
@@ -395,7 +395,7 @@ bool SampleDescription::ReadWrite(BoxBuffer* buffer) {
       RCHECK(audio_entries.size() == count);
     }
   } else {
-    DCHECK_LT(0, count);
+    DCHECK_LT(0u, count);
     if (type == kVideo) {
       for (uint32 i = 0; i < count; ++i)
         RCHECK(video_entries[i].ReadWrite(buffer));
@@ -548,8 +548,8 @@ bool CompactSampleSize::ReadWrite(BoxBuffer* buffer) {
           sizes[i] = size >> 4;
           sizes[i + 1] = size & 0x0F;
         } else {
-          DCHECK_LT(sizes[i], 16);
-          DCHECK_LT(sizes[i + 1], 16);
+          DCHECK_LT(sizes[i], 16u);
+          DCHECK_LT(sizes[i + 1], 16u);
           uint8 size = (sizes[i] << 4) | sizes[i + 1];
           RCHECK(buffer->ReadWriteUInt8(&size));
         }
@@ -778,7 +778,7 @@ HandlerReference::~HandlerReference() {}
 FourCC HandlerReference::BoxType() const { return FOURCC_HDLR; }
 
 bool HandlerReference::ReadWrite(BoxBuffer* buffer) {
-  FourCC hdlr_type;
+  FourCC hdlr_type = FOURCC_NULL;
   std::vector<uint8> handler_name;
   if (!buffer->Reading()) {
     if (type == kVideo) {
@@ -791,6 +791,7 @@ bool HandlerReference::ReadWrite(BoxBuffer* buffer) {
                           kAudioHandlerName + arraysize(kAudioHandlerName));
     } else {
       NOTIMPLEMENTED();
+      return false;
     }
   }
   RCHECK(FullBox::ReadWrite(buffer) &&
diff --git a/media/mp4/box_definitions_unittest.cc b/media/mp4/box_definitions_unittest.cc
index 5169fa4a06..cf29e02d62 100644
--- a/media/mp4/box_definitions_unittest.cc
+++ b/media/mp4/box_definitions_unittest.cc
@@ -787,9 +787,9 @@ TYPED_TEST(BoxDefinitionsTestGeneral, Empty) {
   TypeParam box;
   LOG(INFO) << "Processing " << FourCCToString(box.BoxType());
   if (this->IsOptional(&box)) {
-    ASSERT_EQ(0, box.ComputeSize());
+    ASSERT_EQ(0u, box.ComputeSize());
   } else {
-    ASSERT_NE(0, box.ComputeSize());
+    ASSERT_NE(0u, box.ComputeSize());
   }
 }
 
@@ -837,7 +837,7 @@ TEST_F(BoxDefinitionsTest, TrackFragmentHeader_NoSampleSize) {
 
   TrackFragmentHeader tfhd_readback;
   ASSERT_TRUE(ReadBack(&tfhd_readback));
-  EXPECT_EQ(0, tfhd_readback.default_sample_size);
+  EXPECT_EQ(0u, tfhd_readback.default_sample_size);
   tfhd.default_sample_size = 0;
   ASSERT_EQ(tfhd, tfhd_readback);
 }
diff --git a/media/mp4/box_reader.cc b/media/mp4/box_reader.cc
index 2c6fe5fad3..7f9190906a 100644
--- a/media/mp4/box_reader.cc
+++ b/media/mp4/box_reader.cc
@@ -14,7 +14,7 @@ namespace mp4 {
 BoxReader::BoxReader(const uint8* buf, size_t size)
     : BufferReader(buf, size), type_(FOURCC_NULL), scanned_(false) {
   DCHECK(buf);
-  DCHECK_LT(0, size);
+  DCHECK_LT(0u, size);
 }
 
 BoxReader::~BoxReader() {
@@ -29,7 +29,7 @@ BoxReader::~BoxReader() {
 
 // static
 BoxReader* BoxReader::ReadTopLevelBox(const uint8* buf,
-                                      const int buf_size,
+                                      const size_t buf_size,
                                       bool* err) {
   scoped_ptr<BoxReader> reader(new BoxReader(buf, buf_size));
   if (!reader->ReadHeader(err))
@@ -52,7 +52,7 @@ BoxReader* BoxReader::ReadTopLevelBox(const uint8* buf,
 
 // static
 bool BoxReader::StartTopLevelBox(const uint8* buf,
-                                 const int buf_size,
+                                 const size_t buf_size,
                                  FourCC* type,
                                  int* box_size,
                                  bool* err) {
diff --git a/media/mp4/box_reader.h b/media/mp4/box_reader.h
index 036124d9ae..2a38d36da1 100644
--- a/media/mp4/box_reader.h
+++ b/media/mp4/box_reader.h
@@ -17,7 +17,7 @@
 namespace media {
 namespace mp4 {
 
-class Box;
+struct Box;
 
 /// Class for reading MP4 boxes.
 class BoxReader : public BufferReader {
@@ -35,7 +35,7 @@ class BoxReader : public BufferReader {
   ///         available in the buffer. For MDAT box only, a BoxReader object is
   ///         returned as long as the box header is available.
   static BoxReader* ReadTopLevelBox(const uint8* buf,
-                                    const int buf_size,
+                                    const size_t buf_size,
                                     bool* err);
 
   /// Read the box header from the current buffer.
@@ -48,7 +48,7 @@ class BoxReader : public BufferReader {
   /// @return true if there is enough data to read the header and the header is
   ///         sane, which does not imply that the entire box is in the buffer.
   static bool StartTopLevelBox(const uint8* buf,
-                               const int buf_size,
+                               const size_t buf_size,
                                FourCC* type,
                                int* box_size,
                                bool* err) WARN_UNUSED_RESULT;
diff --git a/media/mp4/chunk_info_iterator_unittest.cc b/media/mp4/chunk_info_iterator_unittest.cc
index 08c997e3db..402ec5bc71 100644
--- a/media/mp4/chunk_info_iterator_unittest.cc
+++ b/media/mp4/chunk_info_iterator_unittest.cc
@@ -59,7 +59,7 @@ TEST_F(ChunkInfoIteratorTest, EmptyChunkInfo) {
   SampleToChunk sample_to_chunk;
   ChunkInfoIterator iterator(sample_to_chunk);
   EXPECT_FALSE(iterator.IsValid());
-  EXPECT_EQ(0, iterator.LastFirstChunk());
+  EXPECT_EQ(0u, iterator.LastFirstChunk());
 }
 
 TEST_F(ChunkInfoIteratorTest, LastFirstChunk) {
diff --git a/media/mp4/composition_offset_iterator.cc b/media/mp4/composition_offset_iterator.cc
index 7c66513f59..60b8f3064c 100644
--- a/media/mp4/composition_offset_iterator.cc
+++ b/media/mp4/composition_offset_iterator.cc
@@ -34,7 +34,7 @@ bool CompositionOffsetIterator::IsValid() const {
          sample_index_ < iterator_->sample_count;
 }
 
-uint32 CompositionOffsetIterator::SampleOffset(uint32 sample) const {
+int32 CompositionOffsetIterator::SampleOffset(uint32 sample) const {
   uint32 current_sample = 0;
   std::vector<CompositionOffset>::const_iterator it =
       composition_offset_table_.begin();
diff --git a/media/mp4/composition_offset_iterator.h b/media/mp4/composition_offset_iterator.h
index d6e89dfbdb..ce4db69c6d 100644
--- a/media/mp4/composition_offset_iterator.h
+++ b/media/mp4/composition_offset_iterator.h
@@ -33,10 +33,10 @@ class CompositionOffsetIterator {
   bool IsValid() const;
 
   /// @return Sample offset for current sample.
-  uint32 sample_offset() const { return iterator_->sample_offset; }
+  int32 sample_offset() const { return iterator_->sample_offset; }
 
   /// @return Sample offset @a sample, 1-based.
-  uint32 SampleOffset(uint32 sample) const;
+  int32 SampleOffset(uint32 sample) const;
 
   /// @return Total number of samples.
   uint32 NumSamples() const;
diff --git a/media/mp4/composition_offset_iterator_unittest.cc b/media/mp4/composition_offset_iterator_unittest.cc
index 848070c44b..88d825388e 100644
--- a/media/mp4/composition_offset_iterator_unittest.cc
+++ b/media/mp4/composition_offset_iterator_unittest.cc
@@ -13,13 +13,12 @@ namespace media {
 namespace mp4 {
 
 const CompositionOffset kCompositionOffsets[] =
-    {{10, 8}, {9, 5}, {25, 7}, {48, 63}, {8, 2}};
+    {{10, -8}, {9, 5}, {25, 7}, {48, 63}, {8, 2}};
 
 class CompositionOffsetIteratorTest : public testing::Test {
  public:
   CompositionOffsetIteratorTest() {
     // Build composition offset table from kCompositionOffsets.
-    uint32 composition_offset = 0;
     uint32 length = sizeof(kCompositionOffsets) / sizeof(CompositionOffset);
     for (uint32 i = 0; i < length; ++i) {
       for (uint32 j = 0; j < kCompositionOffsets[i].sample_count; ++j) {
@@ -35,7 +34,7 @@ class CompositionOffsetIteratorTest : public testing::Test {
   }
 
  protected:
-  std::vector<uint32> composition_offset_table_;
+  std::vector<int32> composition_offset_table_;
   CompositionTimeToSample composition_time_to_sample_;
   scoped_ptr<CompositionOffsetIterator> composition_offset_iterator_;
 
@@ -47,7 +46,7 @@ TEST_F(CompositionOffsetIteratorTest, EmptyCompositionTime) {
   CompositionTimeToSample composition_time_to_sample;
   CompositionOffsetIterator iterator(composition_time_to_sample);
   EXPECT_FALSE(iterator.IsValid());
-  EXPECT_EQ(0, iterator.NumSamples());
+  EXPECT_EQ(0u, iterator.NumSamples());
 }
 
 TEST_F(CompositionOffsetIteratorTest, NumSamples) {
diff --git a/media/mp4/decoding_time_iterator_unittest.cc b/media/mp4/decoding_time_iterator_unittest.cc
index 5bb30964a8..c5e5eecacd 100644
--- a/media/mp4/decoding_time_iterator_unittest.cc
+++ b/media/mp4/decoding_time_iterator_unittest.cc
@@ -47,7 +47,7 @@ TEST_F(DecodingTimeIteratorTest, EmptyDecodingTime) {
   DecodingTimeToSample decoding_time_to_sample;
   DecodingTimeIterator iterator(decoding_time_to_sample);
   EXPECT_FALSE(iterator.IsValid());
-  EXPECT_EQ(0, iterator.NumSamples());
+  EXPECT_EQ(0u, iterator.NumSamples());
 }
 
 TEST_F(DecodingTimeIteratorTest, NumSamples) {
diff --git a/media/mp4/mp4.gyp b/media/mp4/mp4.gyp
index f3b27732b9..f6b211a0ce 100644
--- a/media/mp4/mp4.gyp
+++ b/media/mp4/mp4.gyp
@@ -5,6 +5,10 @@
 # https://developers.google.com/open-source/licenses/bsd
 
 {
+  'variables': {
+    # Compile as chromium code to enable warnings and warnings-as-errors.
+    'chromium_code': 1,
+  },
   'target_defaults': {
     'include_dirs': [
       '../..',
diff --git a/media/mp4/mp4_fragmenter.cc b/media/mp4/mp4_fragmenter.cc
index 283680164c..a1b9f9c879 100644
--- a/media/mp4/mp4_fragmenter.cc
+++ b/media/mp4/mp4_fragmenter.cc
@@ -14,7 +14,7 @@
 #include "media/mp4/cenc.h"
 
 namespace {
-const uint64 kInvalidTime = kuint64max;
+const int64 kInvalidTime = kint64max;
 
 // Optimize sample entries table. If all values in |entries| are identical,
 // then |entries| is cleared and the value is assigned to |default_value|;
diff --git a/media/mp4/mp4_fragmenter.h b/media/mp4/mp4_fragmenter.h
index adb72588b8..528e2772b3 100644
--- a/media/mp4/mp4_fragmenter.h
+++ b/media/mp4/mp4_fragmenter.h
@@ -21,8 +21,8 @@ class MediaSample;
 
 namespace mp4 {
 
-class SegmentReference;
-class TrackFragment;
+struct SegmentReference;
+struct TrackFragment;
 
 /// MP4Fragmenter is responsible for the generation of MP4 fragments, i.e. traf
 /// box and corresponding mdat box. The samples are also encrypted if encryption
@@ -46,7 +46,7 @@ class MP4Fragmenter {
   ~MP4Fragmenter();
 
   /// Add a sample to the fragmenter.
-  virtual Status AddSample(scoped_refptr<MediaSample> sample);
+  Status AddSample(scoped_refptr<MediaSample> sample);
 
   /// Initialize the fragment with default data.
   void InitializeFragment();
@@ -91,8 +91,8 @@ class MP4Fragmenter {
   uint64 fragment_duration_;
   bool normalize_presentation_timestamp_;
   int64 presentation_start_time_;
-  uint64 earliest_presentation_time_;
-  uint64 first_sap_time_;
+  int64 earliest_presentation_time_;
+  int64 first_sap_time_;
   int64 clear_time_;
   scoped_ptr<BufferWriter> data_;
   scoped_ptr<BufferWriter> aux_data_;
diff --git a/media/mp4/mp4_media_parser.h b/media/mp4/mp4_media_parser.h
index a744efc368..7a729e58bf 100644
--- a/media/mp4/mp4_media_parser.h
+++ b/media/mp4/mp4_media_parser.h
@@ -20,10 +20,10 @@ namespace media {
 
 namespace mp4 {
 
-struct Movie;
 class BoxReader;
-class ProtectionSystemSpecificHeader;
 class TrackRunIterator;
+struct Movie;
+struct ProtectionSystemSpecificHeader;
 
 class MP4MediaParser : public MediaParser {
  public:
diff --git a/media/mp4/mp4_segmenter.cc b/media/mp4/mp4_segmenter.cc
index 53c7c87003..edadcf9f0a 100644
--- a/media/mp4/mp4_segmenter.cc
+++ b/media/mp4/mp4_segmenter.cc
@@ -31,10 +31,10 @@ MP4Segmenter::MP4Segmenter(const MuxerOptions& options,
                            scoped_ptr<FileType> ftyp,
                            scoped_ptr<Movie> moov)
     : options_(options),
-      fragment_buffer_(new BufferWriter()),
       ftyp_(ftyp.Pass()),
       moov_(moov.Pass()),
       moof_(new MovieFragment()),
+      fragment_buffer_(new BufferWriter()),
       sidx_(new SegmentIndex()),
       segment_initialized_(false),
       end_of_segment_(false) {}
@@ -44,7 +44,7 @@ MP4Segmenter::~MP4Segmenter() { STLDeleteElements(&fragmenters_); }
 Status MP4Segmenter::Initialize(EncryptorSource* encryptor_source,
                                 double clear_lead_in_seconds,
                                 const std::vector<MediaStream*>& streams) {
-  DCHECK_LT(0, streams.size());
+  DCHECK_LT(0u, streams.size());
   moof_->header.sequence_number = 0;
 
   moof_->tracks.resize(streams.size());
diff --git a/media/mp4/track_run_iterator.cc b/media/mp4/track_run_iterator.cc
index c8b83ced5d..0ae7eeb284 100644
--- a/media/mp4/track_run_iterator.cc
+++ b/media/mp4/track_run_iterator.cc
@@ -172,7 +172,6 @@ bool TrackRunIterator::Init() {
         trak->media.information.sample_table.chunk_large_offset.offsets;
 
     int64 run_start_dts = 0;
-    int64 run_data_offset = 0;
 
     uint32 num_samples = sample_size.sample_count;
     uint32 num_chunks = chunk_offset_vector.size();
diff --git a/media/test/media_test.gyp b/media/test/media_test.gyp
index f1ad4254a2..b5c3f742f1 100644
--- a/media/test/media_test.gyp
+++ b/media/test/media_test.gyp
@@ -5,6 +5,10 @@
 # https://developers.google.com/open-source/licenses/bsd
 
 {
+  'variables': {
+    # Compile as chromium code to enable warnings and warnings-as-errors.
+    'chromium_code': 1,
+  },
   'target_defaults': {
     'include_dirs': [
       '../..',
diff --git a/media/test/packager_test.cc b/media/test/packager_test.cc
index 3fa0f3ef0f..6171dd41b0 100644
--- a/media/test/packager_test.cc
+++ b/media/test/packager_test.cc
@@ -206,7 +206,7 @@ TEST_P(PackagerTestBasic, MP4MuxerSingleSegmentEncrypted) {
   // Expect the output to be encrypted.
   Demuxer demuxer(GetFullPath(kOutputVideo), decryptor_source_);
   ASSERT_OK(demuxer.Initialize());
-  ASSERT_EQ(1, demuxer.streams().size());
+  ASSERT_EQ(1u, demuxer.streams().size());
   EXPECT_TRUE(demuxer.streams()[0]->info()->is_encrypted());
 }
 
@@ -279,7 +279,7 @@ TEST_P(PackagerTest, MP4MuxerMultipleSegmentsUnencrypted) {
     ASSERT_TRUE(base::ReadFileToString(segment_path, &segment_content));
     int bytes_written = file_util::AppendToFile(
         output_path, segment_content.data(), segment_content.size());
-    ASSERT_EQ(segment_content.size(), bytes_written);
+    ASSERT_EQ(segment_content.size(), static_cast<size_t>(bytes_written));
 
     ++segment_index;
   }
diff --git a/mpd/base/mpd_builder_unittest.cc b/mpd/base/mpd_builder_unittest.cc
index 624003a98c..6317882ce3 100644
--- a/mpd/base/mpd_builder_unittest.cc
+++ b/mpd/base/mpd_builder_unittest.cc
@@ -41,7 +41,7 @@ TEST_F(StaticMpdBuilderTest, Video) {
 
   Representation* video_representation =
       video_adaptation_set->AddRepresentation(video_media_info);
-  ASSERT_TRUE(video_adaptation_set);
+  ASSERT_TRUE(video_representation);
 
   EXPECT_NO_FATAL_FAILURE(CheckMpd(kFileNameExpectedMpdOutputVideo1));
 }
@@ -63,7 +63,7 @@ TEST_F(StaticMpdBuilderTest, VideoAndAudio) {
 
   Representation* video_representation =
       video_adaptation_set->AddRepresentation(video_media_info);
-  ASSERT_TRUE(video_adaptation_set);
+  ASSERT_TRUE(video_representation);
 
   EXPECT_NO_FATAL_FAILURE(CheckMpd(kFileNameExpectedMpdOutputAudio1AndVideo1));
 }
diff --git a/mpd/base/mpd_utils.h b/mpd/base/mpd_utils.h
index 6f0d34b84e..3a478b7048 100644
--- a/mpd/base/mpd_utils.h
+++ b/mpd/base/mpd_utils.h
@@ -17,7 +17,7 @@
 
 namespace dash_packager {
 
-class ContentProtectionElement;
+struct ContentProtectionElement;
 
 bool HasVODOnlyFields(const MediaInfo& media_info);
 
diff --git a/mpd/base/xml/xml_node.cc b/mpd/base/xml/xml_node.cc
index 4e2d297ed4..e311c96cc6 100644
--- a/mpd/base/xml/xml_node.cc
+++ b/mpd/base/xml/xml_node.cc
@@ -171,7 +171,7 @@ bool XmlNode::AddChild(ScopedXmlPtr<xmlNode>::type child) {
 
   // Reaching here means the ownership of |child| transfered to |node_|.
   // Release the pointer so that it doesn't get destructed in this scope.
-  child.release();
+  ignore_result(child.release());
   return true;
 }
 
diff --git a/mpd/mpd.gyp b/mpd/mpd.gyp
index 06fb119356..4cbc1fae82 100644
--- a/mpd/mpd.gyp
+++ b/mpd/mpd.gyp
@@ -7,6 +7,10 @@
 # GYP file for any MPD generation targets.
 
 {
+  'variables': {
+    # Compile as chromium code to enable warnings and warnings-as-errors.
+    'chromium_code': 1,
+  },
   'target_defaults': {
     'include_dirs': [
       '..',
diff --git a/packager.gyp b/packager.gyp
index ea1f887d66..723f2e9dd5 100644
--- a/packager.gyp
+++ b/packager.gyp
@@ -5,6 +5,10 @@
 # https://developers.google.com/open-source/licenses/bsd
 
 {
+  'variables': {
+    # Compile as chromium code to enable warnings and warnings-as-errors.
+    'chromium_code': 1,
+  },
   'target_defaults': {
     'include_dirs': [
       '.',