Use Shadow DOM to display fallback content for images

Source/core/html/HTMLInputElement.h

Index: Source/core/html/HTMLInputElement.h
diff --git a/Source/core/html/HTMLInputElement.h b/Source/core/html/HTMLInputElement.h
index 5e77d41f929371b97c01fb303dfe7fa04c2aea71..9696deb66da4276c7a817aa8bd5ce3c17b0fac98 100644
--- a/Source/core/html/HTMLInputElement.h
+++ b/Source/core/html/HTMLInputElement.h
@@ -153,7 +153,7 @@ public:
     virtual bool isActivatedSubmit() const OVERRIDE FINAL;
     virtual void setActivatedSubmit(bool flag) OVERRIDE FINAL;
 
-    String altText() const;
+    virtual String altText() const OVERRIDE FINAL;
 
     int maxResults() const { return m_maxResults; }
 
@@ -249,6 +249,8 @@ public:
     AXObject* popupRootAXObject();
     virtual void didNotifySubtreeInsertionsToDocument() OVERRIDE;
 
+    virtual void ensureFallbackContent() OVERRIDE FINAL;
+    virtual void ensurePrimaryContent() OVERRIDE FINAL;
 protected:
     HTMLInputElement(Document&, HTMLFormElement*, bool createdByParser);
 
@@ -343,9 +345,7 @@ private:
     RadioButtonGroupScope* radioButtonGroupScope() const;
     void addToRadioButtonGroup();
     void removeFromRadioButtonGroup();
-#if ENABLE(INPUT_MULTIPLE_FIELDS_UI)
     virtual PassRefPtr<RenderStyle> customStyleForRenderer() OVERRIDE;
-#endif
 
     virtual bool shouldDispatchFormControlChangeEvent(String&, String&) OVERRIDE;