Cache cc::SharedBitmaps used by PepperGraphics2DHost to upload

Cache cc::SharedBitmaps used by PepperGraphics2DHost to upload

Caching these saves time recreating and remapping them.

Committed: https://crrev.com/4d6eee4bacef37620b88cb698d20244d5173f348
Cr-Commit-Position: refs/heads/master@{#296778}

[jbauman, 2014-09-24 23:32:37]

jbauman@chromium.org changed reviewers:
+ piman@chromium.org

[jbauman, 2014-09-25 05:50:12]

PTAL. Got rid of the timer, but added a few other mechanisms to try to clear the
cache if it's not useful.

[piman, 2014-09-25 17:38:44]

LGTM, thanks!

[jbauman, 2014-09-25 20:07:37]

The CQ bit was checked by jbauman@chromium.org

[commit-bot: I haz the power, 2014-09-25 20:08:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/600953003/20001

[commit-bot: I haz the power, 2014-09-25 20:13:01]

Committed patchset #2 (id:20001) as 8e19dc82d91380b95987dec3c8c44174464109a5

[commit-bot: I haz the power, 2014-09-25 20:13:37]

Patchset 2 (id:??) landed as
https://crrev.com/4d6eee4bacef37620b88cb698d20244d5173f348
Cr-Commit-Position: refs/heads/master@{#296778}