This is a subset CL of the crrev.com/
14731027, and
counter part is crrev.com/
15367003.
I'll send another CL that hooks them once both are landed.
* Add SoftwareMirroringController that implements software based mirroring.
* EnterStateOrFallbackToSoftwareMirroring will try to
fallback software mirroring if the hardware based
mirroring failed.
BUG=239776
TEST=covered by test
Review URL: https://chromiumcodereview.appspot.com/
15448004
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@201554 0039d316-1c4b-4281-b951-d872f2087c98