Make classes and structures in web fast-allocated.

Source/web/WebGraphicsContextImpl.h

Index: Source/web/WebGraphicsContextImpl.h
diff --git a/Source/web/WebGraphicsContextImpl.h b/Source/web/WebGraphicsContextImpl.h
index 954107656cc8dc6165d4e122bd09583e2697328b..60a23225029d21165e620181d222d96f52fb00c3 100644
--- a/Source/web/WebGraphicsContextImpl.h
+++ b/Source/web/WebGraphicsContextImpl.h
@@ -8,6 +8,7 @@
 #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 {
@@ -18,7 +19,8 @@ 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();