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

third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WebGL2RenderingContextBase_h
 #define WebGL2RenderingContextBase_h
 
 #include "modules/webgl/WebGLExtension.h"
 #include "modules/webgl/WebGLRenderingContextBase.h"
 
 namespace blink {
 
 class WebGLTexture;
 
 class WebGLActiveInfo;
 class WebGLBuffer;
 class WebGLProgram;
 class WebGLQuery;
 class WebGLSampler;
 class WebGLSync;
 class WebGLTransformFeedback;
 class WebGLUniformLocation;
 class WebGLVertexArrayObject;
 
 class WebGL2RenderingContextBase : public WebGLRenderingContextBase {
-    USING_GARBAGE_COLLECTED_MIXIN(WebGL2RenderingContextBase);
 public:
     ~WebGL2RenderingContextBase() override;
 
     /* Buffer objects */
     void copyBufferSubData(GLenum, GLenum, long long, long long, long long);
     void getBufferSubData(GLenum target, long long offset, DOMArrayBuffer* returnedData);
 
     /* Framebuffer objects */
     bool validateTexFuncLayer(const char*, GLenum texTarget, GLint layer);
     void blitFramebuffer(GLint, GLint, GLint, GLint, GLint, GLint, GLint, GLint, GLbitfield, GLenum);
@@ skipping 277 matching lines @@
     GLint m_unpackSkipImages;
 };
 
 DEFINE_TYPE_CASTS(WebGL2RenderingContextBase, CanvasRenderingContext, context,
     context->is3d() && WebGLRenderingContextBase::getWebGLVersion(context) >= 2,
     context.is3d() && WebGLRenderingContextBase::getWebGLVersion(&context) >= 2);
 
 } // namespace blink
 
 #endif