GitLab

Fixes a few tests were broken by minor changes in behavior 
introduced in http://crrev.com/220164.

BUG=281730
TEST=MediaSourcePlayerTest.StartTimeTicksResetAfterDecoderUnderruns
     and MediaSourcePlayerTest.ReadFromDemuxerAfterSeek pass now.

Review URL: https://chromiumcodereview.appspot.com/23620012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@221781 0039d316-1c4b-4281-b951-d872f2087c98