Fix flaky fast/events/touch/compositor-touch-hit-rects-scroll.html

Fix flaky fast/events/touch/compositor-touch-hit-rects-scroll.html

1. We expect children of overflow div to be part of scrollingContent
layer to mark it as "scrolling" in the expected output. And also
expect the hit-test rect to be relative to the scrollingContent layer
to make the visualization correct. There is case where the scrolling
element lives in a separate GraphicsLayer than the scrollingContent
layer and mark scrollingCotent layer as its scroll parent. We want
to detect this case and also mark the element as "scrolling" in the
test output. And we also adjust the hit-test rect to be relative to
the scrollingContent layer to make the visualization to work.

2. Because there is a div with negative z-index in the page, compositor
forms a new layer "LayoutBlockFlow HTML" which, instead of the root
document layer, becomes the parent of all the test divs. So we see that
overflowwithborder has a hit-test rect in the space of "HTML", instead
of "#document". We just need to rebaseline for this.

BUG=339118
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=196914

[miletus1, 2015-05-29 16:03:08]

miletus@google.com changed reviewers:
+ rbyers@chromium.org

[miletus1, 2015-05-29 16:03:32]

miletus@google.com changed reviewers:
+ miletus@google.com

[Rick Byers, 2015-06-11 03:22:44]

Whoa, just realized I totally missed this review - sorry! LGTM

[miletus1, 2015-06-11 03:35:17]

The CQ bit was checked by miletus@google.com

[commit-bot: I haz the power, 2015-06-11 03:35:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1158033007/1

[commit-bot: I haz the power, 2015-06-11 05:51:21]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=196914