2D canvas: remain in deferred rendering mode with canvas to canvas drawImage

2D canvas: remain in deferred rendering mode with canvas to canvas drawImage

If the source canvas is not animated, no need to exit deferred rendering
because there is no risk of memory bloat due to snapshotting.

BUG=521001
TEST=telemetry tough_canvas_cases

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200654

[Justin Novosad, 2015-08-17 14:35:28]

junov@chromium.org changed reviewers:
+ senorblanco@chromium.org

[Stephen White, 2015-08-17 15:15:07]

Nice optimization!

https://codereview.chromium.org/1288773005/diff/1/Source/platform/graphics/Im...
File Source/platform/graphics/ImageBuffer.cpp (right):

https://codereview.chromium.org/1288773005/diff/1/Source/platform/graphics/Im...
Source/platform/graphics/ImageBuffer.cpp:153: m_animationState =
DidAcquireSnapshot;
Naming nit: m_drawnToAfterSnapshot or something like that?

[Justin Novosad, 2015-08-17 16:40:20]

New Patch

[Stephen White, 2015-08-17 16:41:27]

LGTM

[Justin Novosad, 2015-08-17 16:54:22]

The CQ bit was checked by junov@chromium.org

[commit-bot: I haz the power, 2015-08-17 16:54:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1288773005/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1288773005/20001

[commit-bot: I haz the power, 2015-08-17 18:06:32]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=200654

[leviw_travelin_and_unemployed, 2015-08-17 19:01:24]

A revert of this CL (patchset #2 id:20001) has been created in
https://codereview.chromium.org/1295673003/ by leviw@chromium.org.

The reason for reverting is: Appears to be triggering MSAN crashes:
http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=vir....