Delete char32 from base/basictypes.h.

(Convert its one use to use int32_t instead.)

R=brettw@chromium.org
TBR=rsleevi@chromium.org
BUG=138542

Review URL: https://codereview.chromium.org/125103006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243209 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243209
Use decoder's timestamp instead of the timestamp from AU during prerolling

When prerolling happens, MediaDecoderJob currently rolls to the timestamp from the access unit.
However, for video, the access unit's timestamp may not match that from the decoder due to reordering.
Even worse, the unit's timestamp may be greatly ahead of the presentation timestamp from the decoder since the decoder is still decoding previous access units. Some of the unit tests actually show this problem.

Fixed all the problematic unit tests along with this CL.

BUG=310823

Review URL: https://codereview.chromium.org/113963005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243210 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243210