Enable WebGL on Windows.

Enable WebGL on Windows.
https://bugs.webkit.org/show_bug.cgi?id=133503

Reviewed by Brent Fulgham.

Source/ThirdParty/ANGLE:
* changes.diff
Recorded additional changes from ANGLE.
* ANGLE.vcxproj/libEGL.vcxproj:
* ANGLE.vcxproj/libEGL.vcxproj.filters:
* ANGLE.vcxproj/libGLESv2.vcxproj:
* ANGLE.vcxproj/libGLESv2.vcxproj.filters:
* include/EGL/egl.h:
* include/EGL/eglsoftlinking.h: Added.
* include/GLES2/gl2.h:
* include/GLES2/gl2softlinking.h: Added.
Resurrected soft linking headers from r153664.
* src/libGLESv2/renderer/VertexBuffer.cpp:
(rx::VertexBufferInterface::directStoragePossible):
Compile fix for Win64.

Source/WebCore:
No new tests, but we should enable the webgl tests soon.

* html/canvas/WebGLRenderingContext.cpp:
(WebCore::WebGLRenderingContext::markContextChanged):
Check if the context and RenderBox are accelerated to use accelerated code path.
* html/canvas/WebGLRenderingContext.h:
Disable accelerated compositing on WebGL canvases until that works.
* platform/graphics/opengl/GraphicsContext3DOpenGLES.cpp:
(WebCore::GraphicsContext3D::reshapeFBOs):
Compile fix after r166563.

Source/WebKit:
* WebKit.vcxproj/WebKit.sln:
Build ANGLE projects and add them as a dependency for linking WebKit.dll.
* WebKit.vcxproj/WebKit/WebKitCommon.props:
Link to ANGLE libraries to get EGL, GLESv2, and GLSL translator symbols.
* WebKit.vcxproj/WebKitExportGenerator/WebKitExports.def.in:
Added 64-bit linker symbol.

Source/WTF:
* wtf/FeatureDefines.h:
Enable WebGL for AppleWin and WinCairo ports.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@169601 268f45cc-cd09-0410-ab3c-d52691b4dbfc