Support author Shadow DOM for INPUT elements

Source/core/dom/Element.h

Index: Source/core/dom/Element.h
diff --git a/Source/core/dom/Element.h b/Source/core/dom/Element.h
index 55c5b0b8566246eabd75ecfc5f1c0ebc859d752a..76f2441b253e33271c46b8e2d3c5d379a677046d 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -444,7 +444,7 @@ public:
     ShadowRoot* shadowRoot() const;
 
     bool hasAuthorShadowRoot() const { return shadowRoot(); }
-
+    virtual void didAddShadowRoot(ShadowRoot&);

[Hajime Morrita, 2013/09/10 06:35:59]

It isn't great to have both didAddShadowRoot() and didUserAgentShadowRoot(). 
Can we unify these somehow?

[tkent, 2013/09/10 06:42:35]

We can. We need to update all of existing didAddUserAgentShadowRoot
implementations.

     ShadowRoot* userAgentShadowRoot() const;
     ShadowRoot* ensureUserAgentShadowRoot();
     virtual const AtomicString& shadowPseudoId() const { return !part().isEmpty() ? part() : pseudo(); }