WIP: Option2: Android media: VideoFrame should not store so many sync points.

media/base/video_frame.h

Index: media/base/video_frame.h
diff --git a/media/base/video_frame.h b/media/base/video_frame.h
index a3f296dd548fb489e97f299355adda2c8107bfae..3e709fcb73ed2ac682d5fc6cbca5c24deadd54ce 100644
--- a/media/base/video_frame.h
+++ b/media/base/video_frame.h
@@ -5,7 +5,7 @@
 #ifndef MEDIA_BASE_VIDEO_FRAME_H_
 #define MEDIA_BASE_VIDEO_FRAME_H_
 
-#include <vector>
+#include <map>
 
 #include "base/callback.h"
 #include "base/md5.h"
@@ -85,7 +85,8 @@ class MEDIA_EXPORT VideoFrame : public base::RefCountedThreadSafe<VideoFrame> {
 
   // CB to be called on the mailbox backing this frame when the frame is
   // destroyed.
-  typedef base::Callback<void(const std::vector<uint32>&)> ReleaseMailboxCB;
+  typedef base::Callback<void(const std::map<std::string, uint32>&)>
+      ReleaseMailboxCB;
 
   // Wraps a native texture of the given parameters with a VideoFrame.  The
   // backing of the VideoFrame is held in the mailbox held by |mailbox_holder|,
@@ -253,12 +254,14 @@ class MEDIA_EXPORT VideoFrame : public base::RefCountedThreadSafe<VideoFrame> {
     timestamp_ = timestamp;
   }
 
-  // Append |sync_point| into |release_sync_points_| which will be passed to
+  // Append |sync_point| into |release_sync_point_map_| which will be passed to
   // the video decoder when |mailbox_holder_release_cb_| is called so that
   // the video decoder waits for the sync points before reusing the mailbox.
-  // Multiple clients can append multiple sync points on one frame.
+  // This keeps only the latest sync point for each client. If a client appends
+  // two sync points, the previous sync point is overridden.
+  // e.g. WebGL can insert multiple sync points on one frame.
   // This method is thread safe. Both blink and compositor threads can call it.
-  void AppendReleaseSyncPoint(uint32 sync_point);
+  void AppendReleaseSyncPoint(std::string client, uint32 sync_point);
 
   // Used to keep a running hash of seen frames.  Expects an initialized MD5
   // context.  Calls MD5Update with the context and the contents of the frame.
@@ -327,7 +330,7 @@ class MEDIA_EXPORT VideoFrame : public base::RefCountedThreadSafe<VideoFrame> {
   base::TimeDelta timestamp_;
 
   base::Lock release_sync_point_lock_;
-  std::vector<uint32> release_sync_points_;
+  std::map<std::string, uint32> release_sync_point_map_;
 
   const bool end_of_stream_;