[iOS] Use WebGLLayer rather than PlatformLayer in GraphicsContext3D
https://bugs.webkit.org/show_bug.cgi?id=134183

Reviewed by Sam Weinig.

GraphicsContext3D has a reference to a WebGLLayer that was
hidden behind a PlatformLayer. This meant we had to cast it
to use a WebGLLayer method.

* platform/graphics/GraphicsContext3D.h: Replace RefPtr<PlatformLayer>
with RefPtr<WebGLLayer>.
* platform/graphics/mac/GraphicsContext3DMac.mm:
(WebCore::GraphicsContext3D::~GraphicsContext3D): No need to cast.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@170285 268f45cc-cd09-0410-ab3c-d52691b4dbfc
REGRESSION (r170257) http/tests/navigation/javascriptlink-frames.html fails on MountainLion
https://bugs.webkit.org/show_bug.cgi?id=134182

Rebaseline for Mountain Lion.

* platform/mac-mountainlion/TestExpectations: Removed.
* platform/mac-mountainlion/http/tests/navigation/javascriptlink-frames-expected.txt:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@170286 268f45cc-cd09-0410-ab3c-d52691b4dbfc