Reland: Make 2D canvas disable gpu acceleration when getImageData is called

Reland: Make 2D canvas disable gpu acceleration when getImageData is called

In order to optimize performance, GPU-accelerated canvases should
permanently switch out of accalerated mode as soon as
getImageData is called.  The cost of getImageData on the GPU is
so prohibitively high that it almost always outways the benefit
of acceleration.

This is the first time we implement a SW/GPU switch that can happen
after the first frame was presented, which may result in a small one
time glitch due to rendering engine discrepancies. Let's see if we get
any complaints about this.  If there are complaint, we may inhibit
the switch based on what kind of content was rendered to the canvas.

BUG=606688
Committed: https://crrev.com/627ddfd0de197d67567a15191f654b8835408bce
Cr-Commit-Position: refs/heads/master@{#403806}

[Justin Novosad, 2016-07-05 14:25:32]

junov@chromium.org changed reviewers:
+ xidachen@chromium.org, xlai@chromium.org

[Justin Novosad, 2016-07-05 14:25:33]

PTAL.

Only Canvas2DLayerBridge has changed since previous version of this patch.

[xidachen, 2016-07-05 15:32:14]

Looks like you need to rebase?

https://codereview.chromium.org/2123623002/diff/1/third_party/WebKit/Source/p...
File third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.cpp
(right):

https://codereview.chromium.org/2123623002/diff/1/third_party/WebKit/Source/p...
third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.cpp:501: if
(isAccelerated() && !isHibernating() && hint == PreferAcceleration) {
It appears to me that if(isAccelerated()) is not the same as if(m_layer). Could
this happen:
m_accelerationMode != DisableAcceleration && !m_layer && hint ==
PreferAcceleration

If the above happens, isAccelerated() will return true, but m_layer is a nullptr
which is not what we want.

Maybe this: if (m_layer && (m_accelerationMode != DisableAcceleration) && ...)?

I feel like doing if (isAccelerated() && m_layer && ...) makes many duplicate
check.

https://codereview.chromium.org/2123623002/diff/1/third_party/WebKit/Source/p...
third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.cpp:612: if
(isAccelerated()) {
if (m_layer && m_accelerationMode != DisableAcceleration)?

https://codereview.chromium.org/2123623002/diff/1/third_party/WebKit/Source/p...
third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.cpp:741: if
(isAccelerated() && !m_destructionInProgress) {
Same as the above.

https://codereview.chromium.org/2123623002/diff/1/third_party/WebKit/Source/p...
third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.cpp:941: if
(isAccelerated())
Same as the above.

[Justin Novosad, 2016-07-05 15:43:10]

Done.

[xidachen, 2016-07-05 15:45:39]

lgtm

[Justin Novosad, 2016-07-05 16:58:50]

The CQ bit was checked by junov@chromium.org

[Justin Novosad, 2016-07-05 16:58:50]

The patchset sent to the CQ was uploaded after l-g-t-m from
xidachen@chromium.org
Link to the patchset: https://codereview.chromium.org/2123623002/#ps60001
(title: "fix tests")

[commit-bot: I haz the power, 2016-07-05 16:59:01]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-07-05 18:28:19]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2016-07-05 18:28:25]

CQ bit was unchecked.

[commit-bot: I haz the power, 2016-07-05 18:30:07]

Description was changed from

==========
Reland: Make 2D canvas disable gpu acceleration when getImageData is called

In order to optimize performance, GPU-accelerated canvases should
permanently switch out of accalerated mode as soon as
getImageData is called.  The cost of getImageData on the GPU is
so prohibitively high that it almost always outways the benefit
of acceleration.

This is the first time we implement a SW/GPU switch that can happen
after the first frame was presented, which may result in a small one
time glitch due to rendering engine discrepancies. Let's see if we get
any complaints about this.  If there are complaint, we may inhibit
the switch based on what kind of content was rendered to the canvas.

BUG=606688
==========

to

==========
Reland: Make 2D canvas disable gpu acceleration when getImageData is called

In order to optimize performance, GPU-accelerated canvases should
permanently switch out of accalerated mode as soon as
getImageData is called.  The cost of getImageData on the GPU is
so prohibitively high that it almost always outways the benefit
of acceleration.

This is the first time we implement a SW/GPU switch that can happen
after the first frame was presented, which may result in a small one
time glitch due to rendering engine discrepancies. Let's see if we get
any complaints about this.  If there are complaint, we may inhibit
the switch based on what kind of content was rendered to the canvas.

BUG=606688

Committed: https://crrev.com/627ddfd0de197d67567a15191f654b8835408bce
Cr-Commit-Position: refs/heads/master@{#403806}
==========

[commit-bot: I haz the power, 2016-07-05 18:30:09]

Patchset 4 (id:??) landed as
https://crrev.com/627ddfd0de197d67567a15191f654b8835408bce
Cr-Commit-Position: refs/heads/master@{#403806}