Turns out this isn't so hard to do that we need to wait for the
completion of DialogSurface and AVDAv2.

This dramatically improves the fullscreen transition; it's much
faster and does not cause audio jank.

BUG=662251
TEST=enter/exit fullscreen on M+ device.
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2461073002
Cr-Commit-Position: refs/heads/master@{#431114}