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- Reduce multipliers from 0.9/1.1 to 0.95/1.05. The current multipliers
seem too drastic.
- Remove logging that doesn't seem too useful for now.
- Add difference_slope logging. It may be useful to log in which
direction the difference is going and how fast.
- Only set the playback rate in the sync'd case if there is
a difference. Otherwise we're making uncessary calls and causing logspam

BUG=internal 73746352
TEST=On device

Change-Id: If073b98892e84ca8f13435f7322012daeb6ffe1a
Reviewed-on: https://chromium-review.googlesource.com/956877
Commit-Queue: Mina Almasry <almasrymina@chromium.org>
Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542609}