Mojo: More data pipe implementation.

Implement the dispatcher for the producer side
(DataPipeProducerDispatcher); the consumer side will be similar.

Implement most of the base class for the connecting part (DataPipe).
Subclasses will provide implementations for the various cases (both
local, local producer/remote consumer, remote producer/local consumer).

The setup is similar to that for MessagePipe, but factored a bit
differently since the sides aren't symmetric (hence no gain in factoring
out the endpoint code).

R=sky@chromium.org

Review URL: https://codereview.chromium.org/103533008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240774 0039d316-1c4b-4281-b951-d872f2087c98
Cleanup OPUS decoder.  Remove extraneous transforms and copies.

Various cleanups:
- Fixes start trimming after seeks.
- Patches FFmpegDemuxer to workaround FFmpeg pre-stripping codec delay.
- Switches decoding to float on all platforms.
- Decodes directly into the AudioBuffer instead of making a copy.
- Switches various error logs to actually be DLOG(ERROR).
- Various tiny code cleanups.
- Rolls DEPS for a couple more OPUS FFmpeg fixes.

BUG=104241, 166752, 168524, 315165, 328207
TEST=opus decoding still works.

Review URL: https://codereview.chromium.org/100503006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240775 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240774
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240776 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240776