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If we miss a browser frame, reschedule a new COMPOSITE_EVENTUALL, there will be
high latency/jank before the next composite happens, but this will keep the
browser compositor and renderer compositor in sync (low latency mode). While if
we COMPOSITOR_IMMEDIATELY, it could make the browser compositor always one frame
behind renderer compositor (high latency mode).

BUG=379264
TEST=record a trace for the following test:
     scroll on a simple page, first with top control hidden, then transit into showing the
     top control.
     With COMPOSITE_IMMEDIATELY, the latency graph shows that the scroll latency jumps up
     at the point of transition and stays at high latency mode.
     With COMPOSITE_EVENTUALL, the latency graph shows that the scroll latency jumps up
     at the point of transition but comes back to normal after.

Review URL: https://codereview.chromium.org/310873002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@274640 0039d316-1c4b-4281-b951-d872f2087c98