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

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

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 17 matching lines @@
 
 #include "bindings/core/v8/Nullable.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/ScriptValue.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/CoreExport.h"
 #include "core/dom/DOMTypedArray.h"
 #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"
 #include "modules/webgl/WebGLVertexArrayObjectBase.h"
 #include "platform/Timer.h"
 #include "platform/graphics/GraphicsTypes3D.h"
 #include "platform/graphics/ImageBuffer.h"
 #include "platform/graphics/gpu/DrawingBuffer.h"
 #include "platform/graphics/gpu/Extensions3DUtil.h"
 #include "platform/graphics/gpu/WebGLImageConversion.h"
@@ skipping 86 matching lines @@
         // Restore DrawingBuffer if needed
         if (!m_readFramebufferBinding && m_drawingBuffer)
             m_drawingBuffer->restoreFramebufferBindings();
     }
 
 private:
     DrawingBuffer* m_drawingBuffer;
     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;
 
     virtual unsigned version() const = 0;
     virtual String contextName() const = 0;
     virtual void registerContextExtensions() = 0;
 
     virtual void initializeNewContext();
 
     static unsigned getWebGLVersion(const CanvasRenderingContext*);
@@ skipping 446 matching lines @@
     bool m_stencilEnabled;
     GLuint m_stencilMask, m_stencilMaskBack;
     GLint m_stencilFuncRef, m_stencilFuncRefBack; // Note that these are the user specified values, not the internal clamped value.
     GLuint m_stencilFuncMask, m_stencilFuncMaskBack;
 
     bool m_isDepthStencilSupported;
 
     bool m_synthesizedErrorsToConsole;
     int m_numGLErrorsToConsoleAllowed;
 
-    bool m_multisamplingAllowed;
-    bool m_multisamplingObserverRegistered;
-
     unsigned long m_onePlusMaxNonDefaultTextureUnit;
 
     OwnPtr<Extensions3DUtil> m_extensionsUtil;
 
     enum ExtensionFlags {
         ApprovedExtension               = 0x00,
         // Extension that is behind the draft extensions runtime flag:
         DraftExtension                  = 0x01,
     };
 
@@ skipping 428 matching lines @@
     // Later, return the cached value.
     GLint maxDrawBuffers();
     GLint maxColorAttachments();
 
     void setBackDrawBuffer(GLenum);
     void setFramebuffer(GLenum, WebGLFramebuffer*);
 
     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);
 
     // Ensures that the JavaScript wrappers for objects that are
     // latched into the context's state, or which are implicitly
     // linked together (like programs and their attached shaders), are
     // not garbage collected before they should be.
     static void preserveObjectWrapper(ScriptState*, ScriptWrappable* sourceObject, const char* baseName, unsigned long index, ScriptWrappable* targetObject);
     // Called to lazily instantiate the wrapper for the default VAO
@@ skipping 27 matching lines @@
 #endif
 };
 
 DEFINE_TYPE_CASTS(WebGLRenderingContextBase, CanvasRenderingContext, context, context->is3d(), context.is3d());
 
 } // namespace blink
 
 WTF_ALLOW_MOVE_INIT_AND_COMPARE_WITH_MEM_FUNCTIONS(blink::WebGLRenderingContextBase::TextureUnitState);
 
 #endif // WebGLRenderingContextBase_h