Remove the MSAA WebSetting, which is not read or used.

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.h

Index: third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.h
diff --git a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.h b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.h
index a477c75a46dc1cb42f20534e4f2fbb786f326b60..38510b7a85a56450e8d162009956e30569aee2f7 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.h
+++ b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.h
@@ -35,7 +35,6 @@
 #include "core/dom/TypedFlexibleArrayBufferView.h"
 #include "core/html/canvas/CanvasRenderingContext.h"
 #include "core/layout/LayoutBoxModelObject.h"
-#include "core/page/Page.h"
 #include "modules/webgl/WebGLContextAttributes.h"
 #include "modules/webgl/WebGLExtensionName.h"
 #include "modules/webgl/WebGLTexture.h"
@@ -142,8 +141,7 @@ private:
     Member<WebGLFramebuffer> m_readFramebufferBinding;
 };
 
-class MODULES_EXPORT WebGLRenderingContextBase : public CanvasRenderingContext, public Page::MultisamplingChangedObserver {

[danakj, 2016/04/04 22:30:28]

The WebGLRCBase used to subclass Page::MultisamplingChangedObserver, which
subclasses GarbageCollectedMixin.

It also does EAGERLY_FINALIZE() down on line 413.

When I remove the subclass of GarbageCollectedMixin (and the
USING_GARBAGE_COLLECTED_MIXIN), I end up hitting an assert in
~VerifyEagerFinalization():
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

I'm trying to parse the comment, but it seems to say that operator new needs to
be "eagerly finalized" by using DECLARE_EAGER_FINALIZATION_OPERATOR_NEW().

-    USING_GARBAGE_COLLECTED_MIXIN(WebGLRenderingContextBase);
+class MODULES_EXPORT WebGLRenderingContextBase : public CanvasRenderingContext {
 public:
     ~WebGLRenderingContextBase() override;
 
@@ -610,9 +608,6 @@ protected:
     bool m_synthesizedErrorsToConsole;
     int m_numGLErrorsToConsoleAllowed;
 
-    bool m_multisamplingAllowed;
-    bool m_multisamplingObserverRegistered;
-
     unsigned long m_onePlusMaxNonDefaultTextureUnit;
 
     OwnPtr<Extensions3DUtil> m_extensionsUtil;
@@ -1061,8 +1056,6 @@ protected:
     virtual void restoreCurrentFramebuffer();
     void restoreCurrentTexture2D();
 
-    void multisamplingChanged(bool) override;
-
     void findNewMaxNonDefaultTextureUnit();
 
     virtual void renderbufferStorageImpl(GLenum target, GLsizei samples, GLenum internalformat, GLsizei width, GLsizei height, const char* functionName);