diff --git a/media/mp4/chunk_info_iterator.cc b/media/mp4/chunk_info_iterator.cc
index 0edb841849..afdbb9192a 100644
--- a/media/mp4/chunk_info_iterator.cc
+++ b/media/mp4/chunk_info_iterator.cc
@@ -40,24 +40,27 @@ bool ChunkInfoIterator::AdvanceSample() {
   return true;
 }
 
-bool ChunkInfoIterator::IsValid() {
-  return iterator_ != chunk_info_table_.end()
-      && chunk_sample_index_ < iterator_->samples_per_chunk;
+bool ChunkInfoIterator::IsValid() const {
+  return iterator_ != chunk_info_table_.end() &&
+         chunk_sample_index_ < iterator_->samples_per_chunk;
 }
 
-uint32 ChunkInfoIterator::NumSamples(uint32 start_chunk, uint32 end_chunk) {
-  DCHECK(start_chunk <= end_chunk);
+uint32 ChunkInfoIterator::NumSamples(uint32 start_chunk,
+                                     uint32 end_chunk) const {
+  DCHECK_LE(start_chunk, end_chunk);
+
   uint32 last_chunk = 0;
   uint32 num_samples = 0;
   for (std::vector<ChunkInfo>::const_iterator it = chunk_info_table_.begin();
-      it != chunk_info_table_.end(); ++it) {
-    last_chunk = (
-        (it + 1 == chunk_info_table_.end()) ?
-            std::numeric_limits<uint32>::max() : (it + 1)->first_chunk) - 1;
+       it != chunk_info_table_.end();
+       ++it) {
+    last_chunk = (it + 1 == chunk_info_table_.end())
+                     ? std::numeric_limits<uint32>::max()
+                     : (it + 1)->first_chunk - 1;
     if (last_chunk >= start_chunk) {
-      num_samples += (std::min(end_chunk, last_chunk)
-          - std::max(start_chunk, it->first_chunk) + 1)
-          * it->samples_per_chunk;
+      num_samples += (std::min(end_chunk, last_chunk) -
+                      std::max(start_chunk, it->first_chunk) + 1) *
+                     it->samples_per_chunk;
       if (last_chunk >= end_chunk)
         break;
     }
diff --git a/media/mp4/chunk_info_iterator.h b/media/mp4/chunk_info_iterator.h
index 32b4ecb38f..1719f4c990 100644
--- a/media/mp4/chunk_info_iterator.h
+++ b/media/mp4/chunk_info_iterator.h
@@ -31,32 +31,27 @@ class ChunkInfoIterator {
   bool AdvanceSample();
 
   // Return whether the current chunk is valid.
-  bool IsValid();
+  bool IsValid() const;
 
   // Return current chunk.
-  uint32 current_chunk() {
-    return current_chunk_;
-  }
+  uint32 current_chunk() const { return current_chunk_; }
 
   // Return samples per chunk for current chunk.
-  uint32 samples_per_chunk() {
-    return iterator_->samples_per_chunk;
-  }
+  uint32 samples_per_chunk() const { return iterator_->samples_per_chunk; }
 
   // Return sample description index for current chunk.
-  uint32 sample_description_index() {
+  uint32 sample_description_index() const {
     return iterator_->sample_description_index;
   }
 
   // Return number of samples from start_chunk to end_chunk, both 1-based,
   // inclusive.
-  uint32 NumSamples(uint32 start_chunk, uint32 end_chunk);
+  uint32 NumSamples(uint32 start_chunk, uint32 end_chunk) const;
 
   // Return the last first_chunk in chunk_info_table.
-  uint32 LastFirstChunk() {
-    if (chunk_info_table_.size() == 0)
-      return 0;
-    return (chunk_info_table_.end() - 1)->first_chunk;
+  uint32 LastFirstChunk() const {
+    return chunk_info_table_.empty() ? 0
+                                     : chunk_info_table_.back().first_chunk;
   }
 
  private:
diff --git a/media/mp4/composition_offset_iterator.cc b/media/mp4/composition_offset_iterator.cc
index c8d37015c8..c013b2e15d 100644
--- a/media/mp4/composition_offset_iterator.cc
+++ b/media/mp4/composition_offset_iterator.cc
@@ -15,8 +15,7 @@ CompositionOffsetIterator::CompositionOffsetIterator(
     const CompositionTimeToSample& composition_time_to_sample)
     : sample_index_(0),
       composition_offset_table_(composition_time_to_sample.composition_offset),
-      iterator_(composition_offset_table_.begin()) {
-}
+      iterator_(composition_offset_table_.begin()) {}
 
 bool CompositionOffsetIterator::AdvanceSample() {
   ++sample_index_;
@@ -29,12 +28,12 @@ bool CompositionOffsetIterator::AdvanceSample() {
   return true;
 }
 
-bool CompositionOffsetIterator::IsValid() {
-  return iterator_ != composition_offset_table_.end()
-      && sample_index_ < iterator_->sample_count;
+bool CompositionOffsetIterator::IsValid() const {
+  return iterator_ != composition_offset_table_.end() &&
+         sample_index_ < iterator_->sample_count;
 }
 
-uint32 CompositionOffsetIterator::SampleOffset(uint32 sample) {
+uint32 CompositionOffsetIterator::SampleOffset(uint32 sample) const {
   uint32 current_sample = 0;
   std::vector<CompositionOffset>::const_iterator it =
       composition_offset_table_.begin();
@@ -47,7 +46,7 @@ uint32 CompositionOffsetIterator::SampleOffset(uint32 sample) {
   return 0;
 }
 
-uint32 CompositionOffsetIterator::NumSamples() {
+uint32 CompositionOffsetIterator::NumSamples() const {
   uint32 num_samples = 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 4d3f4d7cd2..9bd0e9802f 100644
--- a/media/mp4/composition_offset_iterator.h
+++ b/media/mp4/composition_offset_iterator.h
@@ -29,18 +29,16 @@ class CompositionOffsetIterator {
   bool AdvanceSample();
 
   // Return whether the current sample is valid.
-  bool IsValid();
+  bool IsValid() const;
 
   // Return sample offset for current sample.
-  uint32 sample_offset() {
-    return iterator_->sample_offset;
-  }
+  uint32 sample_offset() const { return iterator_->sample_offset; }
 
   // Return sample offset @ sample, 1-based.
-  uint32 SampleOffset(uint32 sample);
+  uint32 SampleOffset(uint32 sample) const;
 
   // Return total number of samples.
-  uint32 NumSamples();
+  uint32 NumSamples() const;
 
  private:
   uint32 sample_index_;
diff --git a/media/mp4/decoding_time_iterator.cc b/media/mp4/decoding_time_iterator.cc
index 0a96d19826..6250a55f31 100644
--- a/media/mp4/decoding_time_iterator.cc
+++ b/media/mp4/decoding_time_iterator.cc
@@ -17,8 +17,7 @@ DecodingTimeIterator::DecodingTimeIterator(
     const DecodingTimeToSample& decoding_time_to_sample)
     : sample_index_(0),
       decoding_time_table_(decoding_time_to_sample.decoding_time),
-      iterator_(decoding_time_table_.begin()) {
-}
+      iterator_(decoding_time_table_.begin()) {}
 
 bool DecodingTimeIterator::AdvanceSample() {
   ++sample_index_;
@@ -31,13 +30,14 @@ bool DecodingTimeIterator::AdvanceSample() {
   return true;
 }
 
-bool DecodingTimeIterator::IsValid() {
-  return iterator_ != decoding_time_table_.end()
-      && sample_index_ < iterator_->sample_count;
+bool DecodingTimeIterator::IsValid() const {
+  return iterator_ != decoding_time_table_.end() &&
+         sample_index_ < iterator_->sample_count;
 }
 
-uint64 DecodingTimeIterator::Duration(uint32 start_sample, uint32 end_sample) {
-  DCHECK(start_sample <= end_sample);
+uint64 DecodingTimeIterator::Duration(uint32 start_sample,
+                                      uint32 end_sample) const {
+  DCHECK_LE(start_sample, end_sample);
   uint32 current_sample = 0;
   uint32 prev_sample = 0;
   uint64 duration = 0;
@@ -45,8 +45,9 @@ uint64 DecodingTimeIterator::Duration(uint32 start_sample, uint32 end_sample) {
   for (; it != decoding_time_table_.end(); ++it) {
     current_sample += it->sample_count;
     if (current_sample >= start_sample) {
-      duration += (std::min(end_sample, current_sample)
-          - std::max(start_sample, prev_sample + 1) + 1) * it->sample_delta;
+      duration += (std::min(end_sample, current_sample) -
+                   std::max(start_sample, prev_sample + 1) + 1) *
+                  it->sample_delta;
       if (current_sample >= end_sample)
         break;
     }
@@ -55,7 +56,7 @@ uint64 DecodingTimeIterator::Duration(uint32 start_sample, uint32 end_sample) {
   return duration;
 }
 
-uint32 DecodingTimeIterator::NumSamples() {
+uint32 DecodingTimeIterator::NumSamples() const {
   uint32 num_samples = 0;
   std::vector<DecodingTime>::const_iterator it = decoding_time_table_.begin();
   for (; it != decoding_time_table_.end(); ++it) {
diff --git a/media/mp4/decoding_time_iterator.h b/media/mp4/decoding_time_iterator.h
index 4333a88623..4ee7018b40 100644
--- a/media/mp4/decoding_time_iterator.h
+++ b/media/mp4/decoding_time_iterator.h
@@ -29,18 +29,16 @@ class DecodingTimeIterator {
   bool AdvanceSample();
 
   // Return whether the current sample is valid.
-  bool IsValid();
+  bool IsValid() const;
 
   // Return sample delta for current sample.
-  uint32 sample_delta() {
-    return iterator_->sample_delta;
-  }
+  uint32 sample_delta() const { return iterator_->sample_delta; }
 
   // Return duration from start_sample to end_sample, both 1-based, inclusive.
-  uint64 Duration(uint32 start_sample, uint32 end_sample);
+  uint64 Duration(uint32 start_sample, uint32 end_sample) const;
 
   // Return total number of samples in the table.
-  uint32 NumSamples();
+  uint32 NumSamples() const;
 
  private:
   uint32 sample_index_;
diff --git a/media/mp4/sync_sample_iterator.cc b/media/mp4/sync_sample_iterator.cc
index b284f22891..c68a297d63 100644
--- a/media/mp4/sync_sample_iterator.cc
+++ b/media/mp4/sync_sample_iterator.cc
@@ -15,8 +15,7 @@ SyncSampleIterator::SyncSampleIterator(const SyncSample& sync_sample)
     : sample_number_(1),
       sync_sample_vector_(sync_sample.sample_number),
       iterator_(sync_sample_vector_.begin()),
-      is_empty_(iterator_ == sync_sample_vector_.end()) {
-}
+      is_empty_(iterator_ == sync_sample_vector_.end()) {}
 
 bool SyncSampleIterator::AdvanceSample() {
   if (iterator_ != sync_sample_vector_.end() && sample_number_ == *iterator_)
@@ -25,19 +24,19 @@ bool SyncSampleIterator::AdvanceSample() {
   return true;
 }
 
-bool SyncSampleIterator::IsSyncSample() {
+bool SyncSampleIterator::IsSyncSample() const {
   // If the sync sample box is not present, every sample is a sync sample.
   if (is_empty_)
     return true;
   return iterator_ != sync_sample_vector_.end() && sample_number_ == *iterator_;
 }
 
-bool SyncSampleIterator::IsSyncSample(uint32 sample) {
+bool SyncSampleIterator::IsSyncSample(uint32 sample) const {
   // If the sync sample box is not present, every sample is a sync sample.
   if (is_empty_)
     return true;
-  return std::binary_search(sync_sample_vector_.begin(),
-                            sync_sample_vector_.end(), sample);
+  return std::binary_search(
+      sync_sample_vector_.begin(), sync_sample_vector_.end(), sample);
 }
 
 }  // namespace mp4
diff --git a/media/mp4/sync_sample_iterator.h b/media/mp4/sync_sample_iterator.h
index a59694f351..71d479ec3b 100644
--- a/media/mp4/sync_sample_iterator.h
+++ b/media/mp4/sync_sample_iterator.h
@@ -27,10 +27,10 @@ class SyncSampleIterator {
   bool AdvanceSample();
 
   // Return whether the current sample is a sync sample.
-  bool IsSyncSample();
+  bool IsSyncSample() const;
 
   // Return whether sample (1-based) is a sync sample.
-  bool IsSyncSample(uint32 sample);
+  bool IsSyncSample(uint32 sample) const;
 
  private:
   uint32 sample_number_;