Eliminate deferral overhead with canvas to canvas draws

Eliminate deferral overhead with canvas to canvas draws

This fixes a performance regression from r199900 which caused deferred
canvas operations to be flushed all the way down to the GrContext level
every time a canvas to canvas draw was performed. This was significantly
slowing down uses cases the use canvases as sprite atlases. This change
does more that fix the performance regression. By stoping the canvas
from switching back and forth between immediate and deferred rendering,
we get ~2x perf boost in cases where a GPU-accelerated canvas is used
as an atlas.

BUG=517504
TEST=tough_canvas_cases/canvas2d_balls_common/bouncing_balls.html?ball=canvas_sprite&back=canvas
NOTRY=true

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200545

[Justin Novosad, 2015-08-14 14:12:38]

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

[Justin Novosad, 2015-08-14 14:12:38]

PTAL

[Justin Novosad, 2015-08-14 14:15:16]

On 2015/08/14 14:12:38, Justin Novosad wrote:
> PTAL

CanvasDeferralMode will have been short lived. LOL

[Stephen White, 2015-08-14 15:10:48]

https://codereview.chromium.org/1297663002/diff/1/Source/modules/canvas2d/Can...
File Source/modules/canvas2d/CanvasRenderingContext2D.cpp (right):

https://codereview.chromium.org/1297663002/diff/1/Source/modules/canvas2d/Can...
Source/modules/canvas2d/CanvasRenderingContext2D.cpp:1391: // FIXME:
crbug.com/447218
Nit: this bug is marked as fixed. Also, it's about display list canvas.
If it's the right bug, we should add a comment to say that it applies
to deferred canvas mode as well.

[Stephen White, 2015-08-14 15:11:01]

LGTM

[Justin Novosad, 2015-08-14 16:06:35]

The CQ bit was checked by junov@chromium.org

[Justin Novosad, 2015-08-14 16:06:35]

The patchset sent to the CQ was uploaded after l-g-t-m from
senorblanco@chromium.org
Link to the patchset: https://codereview.chromium.org/1297663002/#ps20001
(title: "git cl web")

[commit-bot: I haz the power, 2015-08-14 16:06:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1297663002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1297663002/20001

[commit-bot: I haz the power, 2015-08-14 16:11:15]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=200545