Adding VP8 Alpha support in Media Source

media/webm/webm_constants.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_WEBM_WEBM_CONSTANTS_H_
 #define MEDIA_WEBM_WEBM_CONSTANTS_H_
 
 #include "base/basictypes.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
 // WebM element IDs.
 // This is a subset of the IDs in the Matroska spec.
 // http://www.matroska.org/technical/specs/index.html
 const int kWebMIdAESSettingsCipherMode = 0x47E8;
+const int kWebMIdAlphaMode = 0x53C0;
 const int kWebMIdAspectRatioType = 0x54B3;
 const int kWebMIdAttachedFile = 0x61A7;
 const int kWebMIdAttachmentLink = 0x7446;
 const int kWebMIdAttachments = 0x1941A469;
 const int kWebMIdAudio = 0xE1;
 const int kWebMIdBitDepth = 0x6264;
 const int kWebMIdBlock = 0xA1;
 const int kWebMIdBlockAddID = 0xEE;
 const int kWebMIdBlockAdditions = 0x75A1;
 const int kWebMIdBlockAdditional = 0xA5;
@@ skipping 188 matching lines @@
 const int kWebMTrackTypeDescriptionsOrMetadata = 0x21;
 
 MEDIA_EXPORT extern const char kWebMCodecSubtitles[];
 MEDIA_EXPORT extern const char kWebMCodecCaptions[];
 MEDIA_EXPORT extern const char kWebMCodecDescriptions[];
 MEDIA_EXPORT extern const char kWebMCodecMetadata[];
 
 }  // namespace media
 
 #endif  // MEDIA_WEBM_WEBM_CONSTANTS_H_