Merge 138991

Merge 138991
> Add window.internals.nonFastScrollableRects for testing scrollable areas in fast/slow paths
> https://bugs.webkit.org/show_bug.cgi?id=105546
> 
> Reviewed by James Robinson.
> 
> .:
> 
> Export the new symbol.
> 
> * Source/autotools/symbols.filter:
> 
> Source/WebCore:
> 
> No new tests. Added test API for new tests of other bugs.
> 
> * WebCore.exp.in:
> * page/Page.cpp:
> (WebCore::Page::nonFastScrollableRects):
> (WebCore):
> * page/Page.h:
> (WebCore):
> (Page):
> * page/scrolling/ScrollingCoordinator.cpp:
> (WebCore::ScrollingCoordinator::computeNonFastScrollableRegion): Change to public to allow Page::nonFastScrollableRects to access.
> * page/scrolling/ScrollingCoordinator.h:
> (ScrollingCoordinator):
> * testing/Internals.cpp:
> (WebCore::Internals::nonFastScrollableRects):
> (WebCore):
> * testing/Internals.h:
> * testing/Internals.idl:
> 
> Source/WebKit2:
> 
> Export the new symbol.
> 
> * win/WebKit2.def.in:
> 

TBR=wangxianzhu@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=139631