Subpixel rendering: Animating HTML elements leaves trails when embedded to a subpxiel positioned iframe.

[zalan]

Steps to Reproduce:
1. go to http://www.w3schools.com/jquery/tryit.asp?filename=tryjquery_animation1
2. click on the "Start animation" button on the right panel

[zalan]

rdar://problem/19078958

[zalan]

Created attachment 243374 [details]
Test reduction.

[zalan]

Created attachment 243380 [details]
Patch

[Simon Fraser (smfr)]

Comment on attachment 243380 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=243380&action=review

> Source/WebCore/rendering/RenderBox.cpp:2191
> +    // FIXME: This is needed as long as RenderWidget snaps to integral size/position.
> +    if (isRenderReplaced() && isWidget())
> +        locationOffset = toIntSize(flooredIntPoint(locationOffset));

It would be good to put a comment in RenderWidget referencing this snapping.

Are there any other computeRectForRepaint impls that needs this change?

> LayoutTests/ChangeLog:16
> +        * platform/mac/fast/images/repaint-subrect-grid-expected.txt: repaint rect tracking change.
> +        * platform/mac/fast/repaint/hidpi-absolute-positioned-element-wrong-cliprect-after-move-expected.txt: Added. repaint rect tracking change.
> +        * platform/mac/fast/repaint/hidpi-device-pixel-based-repaint-rect-tracking-expected.txt: Added. repaint rect tracking change.
> +        * platform/mac/fast/repaint/hidpi-transform-on-subpixel-repaintrect-expected.txt: Added. repaint rect tracking change.

These should go in the cross-platform dir.

[Build Bot]

Comment on attachment 243380 [details]
Patch

Attachment 243380 [details] did not pass mac-wk2-ews (mac-wk2):
Output: http://webkit-queues.appspot.com/results/4698876044902400

New failing tests:
fast/repaint/hidpi-content-inside-iframe-leaves-trails.html
fast/repaint/hidpi-transform-on-subpixel-repaintrect.html
fast/repaint/hidpi-absolute-positioned-element-wrong-cliprect-after-move.html
fast/images/repaint-subrect-grid.html
fast/repaint/hidpi-device-pixel-based-repaint-rect-tracking.html

[Build Bot]

Created attachment 243385 [details]
Archive of layout-test-results from ews105 for mac-mountainlion-wk2

The attached test failures were seen while running run-webkit-tests on the mac-wk2-ews.
Bot: ews105  Port: mac-mountainlion-wk2  Platform: Mac OS X 10.8.5

[zalan]

Created attachment 243389 [details]
Patch

[zalan]

Repaint rect tracking behavior change is moved here: bug 139703

[Build Bot]

Comment on attachment 243389 [details]
Patch

Attachment 243389 [details] did not pass mac-wk2-ews (mac-wk2):
Output: http://webkit-queues.appspot.com/results/4530429575036928

New failing tests:
fast/repaint/hidpi-content-inside-iframe-leaves-trails.html

[Build Bot]

Created attachment 243394 [details]
Archive of layout-test-results from ews105 for mac-mountainlion-wk2

The attached test failures were seen while running run-webkit-tests on the mac-wk2-ews.
Bot: ews105  Port: mac-mountainlion-wk2  Platform: Mac OS X 10.8.5

[zalan]

Created attachment 243399 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 243399 [details]
Patch

Clearing flags on attachment: 243399

Committed r177412: <http://trac.webkit.org/changeset/177412>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.