Enable use of MediaDrm by default on Android.

This reverts r227878: "Disable use of MediaDrm by default on Android."

Widevine key system is also enabled with EME on Chrome for Android.

BUG=163552
R=ddorwin@chromium.org, qinmin@chromium.org
TBR=jochen@chromium.org

Review URL: https://codereview.chromium.org/32883003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230139 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230139
cc: Prioritize impl-thread drawing in scheduler in smoothness mode

When the compositor is in prefer smoothness mode, prioritize impl-thread
draws over main thread frames and tree activations in the scheduler.
This makes it less likely for us to drop frames during
smoothness-triggering gestures such as flings and pinch-zooms. The
tradeoff is that main thread updates will have higher latency in these
modes.

BUG=309630

Review URL: https://codereview.chromium.org/35013002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230141 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230141