Simplify and speed up painting of clipping masks

Simplify and speed up painting of clipping masks

To paint the contents of clipping mask layers, we use the full paint machinery including paint offsets, several layers of paint methods in a call hierarchy, layout object queries and more.

All we need to do when we have already processed the clips is to fill the area bounded by the clip rects with black.

This will save all those method calls, and a bunch of if checks that
slow down every other paint operation, and makes border-radius for
composited children much more efficient and less complex.

R=chrishtr@chromium.org
BUG=674977
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

[Stephen Chennney, 2016-12-16 18:06:59]

Description was changed from

==========
Simplify and speed up painting of clipping masks

To paint the contents of clipping mask layers, we use the full paint machinery
including paint offsets, several layers of paint methods in a call hierarchy,
layout object queries and more.

All we need to do is fill the area bounded by the clip rects with black.

This will save all those method calls, and a bunch of if checks that
slow down every other paint operation, and makes border-radius for
composited children much more efficient and less complex.

R=chrishtr@chromium.org
BUG=674977
==========

to

==========
Simplify and speed up painting of clipping masks

To paint the contents of clipping mask layers, we use the full paint machinery
including paint offsets, several layers of paint methods in a call hierarchy,
layout object queries and more.

All we need to do is fill the area bounded by the clip rects with black.

This will save all those method calls, and a bunch of if checks that
slow down every other paint operation, and makes border-radius for
composited children much more efficient and less complex.

R=chrishtr@chromium.org
BUG=674977
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

[Stephen Chennney, 2016-12-16 18:10:19]

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

[Stephen Chennney, 2016-12-16 18:10:52]

I'd like to land this to dramatically simplify the border-radius work, and
generally clean things up a lot regardless.

[commit-bot: I haz the power, 2016-12-16 18:11:03]

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

[Stephen Chennney, 2016-12-16 18:11:43]

Still needs a little work. I'm apparently not catching all the call sites.

[Stephen Chennney, 2016-12-16 19:27:38]

Description was changed from

==========
Simplify and speed up painting of clipping masks

To paint the contents of clipping mask layers, we use the full paint machinery
including paint offsets, several layers of paint methods in a call hierarchy,
layout object queries and more.

All we need to do is fill the area bounded by the clip rects with black.

This will save all those method calls, and a bunch of if checks that
slow down every other paint operation, and makes border-radius for
composited children much more efficient and less complex.

R=chrishtr@chromium.org
BUG=674977
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

to

==========
Simplify and speed up painting of clipping masks

To paint the contents of clipping mask layers, we use the full paint machinery
including paint offsets, several layers of paint methods in a call hierarchy,
layout object queries and more.

All we need to do when we have already processed the clips is to fill the area
bounded by the clip rects with black.

This will save all those method calls, and a bunch of if checks that
slow down every other paint operation, and makes border-radius for
composited children much more efficient and less complex.

R=chrishtr@chromium.org
BUG=674977
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

[Stephen Chennney, 2016-12-16 19:28:00]

The CQ bit was unchecked by schenney@chromium.org

[Stephen Chennney, 2016-12-16 19:55:06]

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

[commit-bot: I haz the power, 2016-12-16 19:55:39]

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

[Stephen Chennney, 2016-12-16 19:56:03]

OK, this works but unfortunately only hits a couple of cases. It seems we
process the clips later in the pipeline for most existing situations. Of course,
that number will blow up when I finally get the border-radius work done.

[commit-bot: I haz the power, 2016-12-17 00:04:14]

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

[commit-bot: I haz the power, 2016-12-17 00:04:15]

Dry run: This issue passed the CQ dry run.

[Stephen Chennney, 2016-12-19 16:37:20]

On 2016/12/16 19:56:03, Stephen Chennney wrote:
> OK, this works but unfortunately only hits a couple of cases. It seems we
> process the clips later in the pipeline for most existing situations. Of
course,
> that number will blow up when I finally get the border-radius work done.

This patch is wrong, which wasn't revealed in testing.