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And use it to flush rendering before page flip.

BUG=412508,442605
TEST=build and run Chrome on jerry/freon. It should render one frame.
R=alexst@chromium.org
R=dnicoara@chromium.org
R=kbr@chromium.org
R=piman@chromium.org
Signed-off-by: Dominik Behr <dbehr@chromium.org>

Review URL: https://codereview.chromium.org/903063003

Cr-Commit-Position: refs/heads/master@{#315171}