Merge 146940 "Non-paintsContent fixed position layer should not ..."

Merge 146940 "Non-paintsContent fixed position layer should not ..."

> Non-paintsContent fixed position layer should not cause slow scrolling
> https://bugs.webkit.org/show_bug.cgi?id=113238
> 
> Reviewed by James Robinson.
> 
> Source/WebCore:
> 
> Added NotCompositedForNoVisibleContent in ViewportConstrainedNotCompositedReason and set it in RLC.
> 
> Test: compositing/layer-creation/fixed-position-no-content-scroll-reason.html
> 
> * rendering/RenderLayer.h: Add NotCompositedForNoVisibleContent.
> * rendering/RenderLayerCompositor.cpp:
> (WebCore::RenderLayerCompositor::requiresCompositingForPosition): Set NotCompositedForNoVisibleContent reason when the fixed position layer has no visible content.
> 
> LayoutTests:
> 
> * compositing/layer-creation/fixed-position-no-content-scroll-reason-expected.txt: Added.
> * compositing/layer-creation/fixed-position-no-content-scroll-reason.html: Copied from LayoutTests/compositing/layer-creation/fixed-position-out-of-view-scroll-reason.html. Test case for the bug.
> * compositing/layer-creation/fixed-position-in-view-dynamic.html: Set background of fixed layer to distinguish out-of-view case from no-content case.
> * compositing/layer-creation/fixed-position-out-of-view-dynamic.html: Ditto.
> * compositing/layer-creation/fixed-position-out-of-view-scroll-reason.html: Ditto.
> * platform/chromium/compositing/layer-creation/fixed-position-in-view-dynamic-expected.txt: Removed. This was a wrong rebaseline related to this bug.
> * platform/chromium/platform/chromium/virtual/softwarecompositing/layer-creation/fixed-position-in-view-dynamic-expected.txt: Removed. This was a wrong rebaseline related to this bug.
> 

TBR=wangxianzhu@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=146959

[Xianzhu, 2013-03-27 02:18:05]

Committed patchset #1 manually as r146959.