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This is partial cl from https://codereview.chromium.org/775143003/
for easy reviewing.
For now, authoritative vsync interval is handled by CompositorVsyncManager.
It will not be used when BeginFrame scheduling is enabled on aura.
Instead, it will be handled by scheduler.
In the next cl, BeginFrame sheduling on aura(and ash) will be turned on.

R=brianderson@chromium.org, mithro@mithis.com
BUG=372086
TEST=cc_unittests

Review URL: https://codereview.chromium.org/1005553004

Cr-Commit-Position: refs/heads/master@{#322125}