Change the GPU process to use a CFRunLoop

This is necessary for CAContext sharing (determined empirically, as
that API is undocumented).

BUG=312462

Review URL: https://codereview.chromium.org/279163005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270309 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed