Add a flag --video_feature for Widevine

Change-Id: Id9ab958add1239972a4f94faf5e65cffe64444be

packager/media/base/media_base.gyp

@@ -120,6 +120,7 @@
         '../../packager.gyp:status',
         '../../third_party/boringssl/boringssl.gyp:boringssl',
         '../../third_party/curl/curl.gyp:libcurl',
+        '../../third_party/gflags/gflags.gyp:gflags',
         '../../third_party/libxml/libxml.gyp:libxml',
         '../../version/version.gyp:version',
       ],

packager/media/base/widevine_common_encryption.proto

@@ -74,6 +74,13 @@ message CommonEncryptionRequest {
 
   // Enable entitlement license if set to true.
   optional bool enable_entitlement_license = 16;
+
+  // Video feature identifier, which is used in conjunction with |content_id|
+  // to derive key IDs and content keys. For example, it can be used to generate
+  // different keys for HDR and SDR. The value is propagated to PSSH.
+  // Ignored for tracks with type “AUDIO”.
+  // Current values are "HDR".
+  optional string video_feature = 19;
 }
 
 message CommonEncryptionResponse {

packager/media/base/widevine_key_source.cc

@@ -6,6 +6,8 @@
 
 #include "packager/media/base/widevine_key_source.h"
 
+#include <gflags/gflags.h>
+
 #include "packager/base/base64.h"
 #include "packager/base/bind.h"
 #include "packager/base/strings/string_number_conversions.h"
@@ -20,6 +22,10 @@
 #include "packager/media/base/request_signer.h"
 #include "packager/media/base/widevine_common_encryption.pb.h"
 
+DEFINE_string(video_feature,
+              "",
+              "Specify the optional video feature, e.g. HDR.");
+
 namespace shaka {
 namespace media {
 namespace {
@@ -364,6 +370,9 @@ void WidevineKeySource::FillRequest(bool enable_key_rotation,
 
   if (!group_id_.empty())
     request->set_group_id(group_id_.data(), group_id_.size());
+
+  if (!FLAGS_video_feature.empty())
+    request->set_video_feature(FLAGS_video_feature);
 }
 
 Status WidevineKeySource::GenerateKeyMessage(