Allow HTMLPlugInElement to host UA shadow DOM.

Source/core/rendering/RenderReplaced.h

Index: Source/core/rendering/RenderReplaced.h
diff --git a/Source/core/rendering/RenderReplaced.h b/Source/core/rendering/RenderReplaced.h
index 2b79164aa57c8c9a32c0c617bcb7f18c81f6e461..8e54995b404a70e4d1817584e142a7818242c24e 100644
--- a/Source/core/rendering/RenderReplaced.h
+++ b/Source/core/rendering/RenderReplaced.h
@@ -40,6 +40,11 @@ public:
 
     virtual bool needsPreferredWidthsRecalculation() const OVERRIDE;
 
+    // These values are specified to be 300 and 150 pixels in the CSS 2.1 spec.
+    // http://www.w3.org/TR/CSS2/visudet.html#inline-replaced-width
+    static const int defaultWidth;
+    static const int defaultHeight;
+
 protected:
     virtual void willBeDestroyed() OVERRIDE;