Re-land: Make 2D canvas smarter about chosing whether or not to use GPU acceleration

Re-land: Make 2D canvas smarter about chosing whether or not to use GPU acceleration

Original patch: https://codereview.chromium.org/1367683002/

The CL takes advantage of the fact that canvas rendering is deferred
to defer the decision of whether or not a canvas should be
GPU-accelerated. The decision is made based on the conditions
under which a canvas is flushed for the first time. For example,
if the purpose of the first flush is to perform a readback, then
GPU-acceleration will be disabled for the canvas in order to avoid
reading GPU memory into RAM, which is known to be a slow path.

BUG=265849
TBR=senorblanco@chromium.org, kbr@chromium.org

Committed: https://crrev.com/8046330d6021c156f59a49729ed2308eda912add
Cr-Commit-Position: refs/heads/master@{#350817}

[Justin Novosad, 2015-09-24 21:58:16]

The CQ bit was checked by junov@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-09-24 21:59:55]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1372463002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1372463002/1

[commit-bot: I haz the power, 2015-09-24 22:12:29]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-09-24 22:12:29]

Dry run: Try jobs failed on following builders:
  mac_chromium_compile_dbg_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)

[Justin Novosad, 2015-09-25 12:38:41]

The CQ bit was checked by junov@chromium.org

[commit-bot: I haz the power, 2015-09-25 12:39:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1372463002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1372463002/20001

[commit-bot: I haz the power, 2015-09-25 13:55:37]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-09-25 13:56:41]

Patchset 2 (id:??) landed as
https://crrev.com/8046330d6021c156f59a49729ed2308eda912add
Cr-Commit-Position: refs/heads/master@{#350817}