cc: Re-enable prepaint for GPU rasterization

cc: Re-enable prepaint for GPU rasterization

The synchronous rasterization change for GPU rasterization tries
to avoid prepainting, which may have caused longer frame times in
some of the tests.

We'll re-enable prepainting to see if this is the reason.  This
will probably be reverted.

Committed: https://crrev.com/dee056c614737f8bf07686d38dfcc4d264c51813
Cr-Commit-Position: refs/heads/master@{#309956}

[hendrikw, 2015-01-05 18:45:29]

hendrikw@chromium.org changed reviewers:
+ vmiura@chromium.org, vmpstr@chromium.org

[hendrikw, 2015-01-05 18:45:29]

PTAL

[vmiura, 2015-01-05 18:58:16]

On 2015/01/05 18:45:29, hendrikw wrote:
> PTAL

LGTM.

[vmpstr, 2015-01-05 19:29:18]

lgtm

[hendrikw, 2015-01-05 19:30:04]

The CQ bit was checked by hendrikw@chromium.org

[commit-bot: I haz the power, 2015-01-05 19:31:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/837533002/1

[commit-bot: I haz the power, 2015-01-05 20:32:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-05 20:33:36]

Patchset 1 (id:??) landed as
https://crrev.com/dee056c614737f8bf07686d38dfcc4d264c51813
Cr-Commit-Position: refs/heads/master@{#309956}

[hendrikw, 2015-01-07 23:21:34]

On 2015/01/05 20:33:36, I haz the power (commit-bot) wrote:
> Patchset 1 (id:??) landed as
> https://crrev.com/dee056c614737f8bf07686d38dfcc4d264c51813
> Cr-Commit-Position: refs/heads/master@{#309956}

It looks like we're not seeing much improvement on the bots with this, so I'm
reverting this, because there is some concern that we could end up rasterizing
too many tiles synchronously.

[hendrikw, 2015-01-07 23:22:34]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/844503004/ by hendrikw@chromium.org.

The reason for reverting is: Better to leave this in, and now we know that this
doesn't improve telemetry significantly.