Make classes and structures in web fast-allocated.

Source/web/WebGraphicsContextImpl.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 WebGraphicsContextImpl_h
 #define WebGraphicsContextImpl_h
 
 #include "platform/graphics/paint/DisplayItem.h"
 #include "platform/graphics/paint/DisplayItemClient.h"
 #include "public/web/WebGraphicsContext.h"
+#include "wtf/Allocator.h"
 #include "wtf/OwnPtr.h"
 
 namespace blink {
 
 class DrawingRecorder;
 class GraphicsContext;
 
 // Wraps a blink::GraphicsContext.
 // Internal consumers can extract the underlying context (via WebGraphicsContextImpl).
 // External consumers can make a single drawing using a WebCanvas.
-class WebGraphicsContextImpl : public WebGraphicsContext {
+class WebGraphicsContextImpl final : public WebGraphicsContext {
+    DISALLOW_ALLOCATION();
 public:
     WebGraphicsContextImpl(GraphicsContext&, const DisplayItemClientWrapper&, DisplayItem::Type);
     ~WebGraphicsContextImpl();
     GraphicsContext& graphicsContext() { return m_graphicsContext; }
 
     // blink::WebGraphicsContext
     WebCanvas* beginDrawing(const WebFloatRect& bounds) override;
     void endDrawing() override;
 
 private:
     GraphicsContext& m_graphicsContext;
     DisplayItemClientWrapper m_client;
     DisplayItem::Type m_type;
     OwnPtr<DrawingRecorder> m_drawingRecorder;
 #ifndef NDEBUG
     bool m_hasBegunDrawing;
 #endif
 };
 
 // Source/web/ assumes that WebGraphicsContextImpl is the only implementation.
 DEFINE_TYPE_CASTS(WebGraphicsContextImpl, WebGraphicsContext, webGraphicsContext, true, true);
 
 } // namespace blink
 
 #endif