Ignore overflow clip on root layer if HitTestRequest::IgnoreClipping is set.

Ignore overflow clip on root layer if HitTestRequest::IgnoreClipping is set.

Previously, DeprecatedPaintLayer::hitTest could choose whether to clip to the
viewport by simply passing the appropriate hitTestRect param to hitTestLayer.
But with root layer scrolling, the viewport clip is reflected in the clip rects
computed by DeprecatedPaintLayerClipper which are cached and propagated down the
layer tree, so it is harder to ignore.

This change teaches DeprecatedPaintLayerClipper how to ignore the viewport clip. 

BUG=499053
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197214

[skobes, 2015-06-16 22:57:48]

skobes@chromium.org changed reviewers:
+ esprehn@chromium.org

[esprehn, 2015-06-16 23:02:02]

lgtm, can you expand the description some about why you need to do this.

Sad we have to make the cache even bigger and more complicated.

https://codereview.chromium.org/1184303003/diff/1/Source/core/layout/ClipRect...
File Source/core/layout/ClipRectsCache.h (right):

https://codereview.chromium.org/1184303003/diff/1/Source/core/layout/ClipRect...
Source/core/layout/ClipRectsCache.h:21:
RootRelativeClipRectsIgnoringViewportClip,
Sigh, this makes every DPL bigger.

[skobes, 2015-06-16 23:28:56]

On 2015/06/16 23:02:02, esprehn wrote:
> lgtm, can you expand the description some about why you need to do this.

Done.

> Sad we have to make the cache even bigger and more complicated.

It's hopefully temporary, since slimming paint v3 will redesign hit testing.

[skobes, 2015-06-16 23:29:02]

The CQ bit was checked by skobes@chromium.org

[commit-bot: I haz the power, 2015-06-16 23:29:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1184303003/1

[commit-bot: I haz the power, 2015-06-17 00:39:27]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197214