ui/compositor: use an IO message loop on posix instead of DEFAULT

MessagePumpDefault breaks PostDelayedTask on posix because it uses system time.
MessagePumpIO uses monotonic time, so is immune to these problems.

BUG=293736,chrome-os-partner:22627

Review URL: https://chromiumcodereview.appspot.com/23691074

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@223961 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed