Notify WebM media segment start when kWebMIdCluster is parsed

Fixes WebM stream parser to conform more closely to MSE segment loop
parser's PARSING_MEDIA_SEGMENT state entrance:
Immediately calls the new segment CB when |kWebMIdCluster| is parsed,
instead of waiting until enough data has been appended and parsed
for the cluster parser to determine the cluster start timestamp.
Adds associated unit tests (for WebM).

R=acolwell@chromium.org
BUG=334127
TEST=All media_unittests and MSE layout tests pass locally on Linux

Review URL: https://codereview.chromium.org/133433005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245728 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245728
Rename some Cast Streaming APIs

Rename done in this change:
chrome.cast.streaming.start -> chrome.cast.streaming.setDestination
chrome.cast.rtpStream.getCaps ->
    chrome.cast.rtpStream.getSupportedParams

Also removed the dictionary of CastRtpCaps. And now there's just one
CastRtpParams.

Review URL: https://codereview.chromium.org/137003003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245729 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245729
Add gpu::MailboxHolder to hold state for a gpu::Mailbox

gpu::Mailbox by itself can hold only a texture id, but in common usage it comes
with texture target and syncpoint information for cross-context sharing.  To
reduce repetition of this pattern, gpu::MailboxHolder holds:

* a gpu::Mailbox
* a GL texture target
* a syncpoint index

Refactor other classes to use a gpu::MailboxHolder instead of separate
gpu::Mailbox and associated state.

Syncpoints are created with uint32 indices; make sure all uses of syncpoints use uint32.

BUG=None
TEST=local build, unittests on CrOS snow, desktop Linux

Review URL: https://codereview.chromium.org/105743004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245730 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245730