Use tiles when encoding with VP9.

Use tiles when encoding with VP9.

VP9's tile encoding feature allows for multithreaded parallelism on both the
encoder and decoder side.

TEST=Run remoting_perftests under VTune and see that two logical CPUs are used
BUG=134202
Committed: https://crrev.com/e67fefbf4f5a5a83ca8d487f422b09664dc4c8fe
Cr-Commit-Position: refs/heads/master@{#319167}

[aconverse, 2015-03-04 21:10:34]

aconverse@chromium.org changed reviewers:
+ wez@chromium.org

[Wez, 2015-03-04 21:23:28]

The CQ bit was checked by wez@chromium.org

[Wez, 2015-03-04 21:23:29]

lgtm

[commit-bot: I haz the power, 2015-03-04 21:24:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/977663004/1

[commit-bot: I haz the power, 2015-03-05 00:12:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-05 00:12:29]

Patchset 1 (id:??) landed as
https://crrev.com/e67fefbf4f5a5a83ca8d487f422b09664dc4c8fe
Cr-Commit-Position: refs/heads/master@{#319167}

[aconverse, 2015-03-05 01:05:10]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/978133002/ by aconverse@chromium.org.

The reason for reverting is: Breaks linux valgrind,
needs libvpx side fixes and roll,
http://build.chromium.org/p/chromium.memory.fyi/builders/Linux%20Tests%20%28v....