Add metadata to media::VideoFrame and plumb it through IPC/MediaStream.

This change has three main goals: First, to be able to pass extra
information associated with each VideoFrame from the capture source to
the downstream consumers (see bugs for details).  Second, to eliminate
redundancies in the current MediaStreamVideoSink API; specifically,
media::VideoFrame contains most of the same properties as
media::VideoCaptureFormat.  Third, to fully support the separate
VideoFrame concepts of "coded size" versus "visible size" in the capture
pipeline, rather than force all producers/consumers to deal with packed
data.  (Using packed frame sizes can be suboptimal for performance in
some use cases.)

The metadata is stored in a base::DictionaryValue owned by
media::VideoFrame to allow for structured data passing.  DictionaryValue
is a great choice since an efficient IPC (de)serialization
implementation already exists, and the metadata can be easily
pretty-printed for logging where needed.  Also, it's logical for
VideoFrame to own the metadata, as both need to be passed/shared
together across threads without copying.

Finally, this change includes one new use of the metadata as a
motivation for its existence: The tab/desktop capture code now includes
capture timing information, which will allow Cast streaming sessions to
be analyzed for user experience improvements.  In the future, some of
the special-use-case data members in VideoFrame should be moved into
the metadata.

BUG=461116,462101

Review URL: https://codereview.chromium.org/955253002

Cr-Commit-Position: refs/heads/master@{#318954}

1 files changed, 0 insertions, 1 deletions

diff --git a/content/renderer/media/media_stream_video_track_unittest.cc b/content/renderer/media/media_stream_video_track_unittest.cc
index eed4fa29..2fe8503 100644
--- a/content/renderer/media/media_stream_video_track_unittest.cc
+++ b/content/renderer/media/media_stream_video_track_unittest.cc
@@ -139,7 +139,6 @@ class CheckThreadHelper {
 void CheckThreadVideoFrameReceiver(
     CheckThreadHelper* helper,
     const scoped_refptr<media::VideoFrame>& frame,
-    const media::VideoCaptureFormat& format,
     const base::TimeTicks& estimated_capture_time) {
   // Do nothing.
 }