GitLab

Adds logic + test to truncate the duration on Media Source streams when
EndOfStream is signalled. Also adds some logic to make sure buffered streams
never exceed the reported duration.

BUG=139899

Review URL: https://chromiumcodereview.appspot.com/10829108

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@149702 0039d316-1c4b-4281-b951-d872f2087c98