Test number of render passes in YUV readback pipeline.

BUG=313046

Review URL: https://codereview.chromium.org/48733010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233055 0039d316-1c4b-4281-b951-d872f2087c98
ChromeOS: Accept NULL SystemBus in MediaTransferProtocolManager.

DBusThreadManager's GetSystemBus returns NULL if Chrome built for ChromeOS runs on Linux or in tests.

BUG=275286

Review URL: https://codereview.chromium.org/57333002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233056 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233055
SVN changes up to revision 233056