Automated Commit: Committing new LKGM version 4928.0.0 for chromeos.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233537 0039d316-1c4b-4281-b951-d872f2087c98
Disable MediaGalleriesPrivateApiTest.DeviceAttachDetachEvents on Linux official bot.

BUG=315276

Review URL: https://codereview.chromium.org/61283002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233538 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233538
Limit pixels that get cleared to repaint area.

Since we now keep the canvas around in the ContentLayerUpdater, we often
end up getting small invalidations that paint on a large canvas. In those
cases, instead of clearing the entire canvas to transparent, clear only the
portion that will be repainted.

BUG=313494

Review URL: https://codereview.chromium.org/61403003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233539 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233539