Bug 836176 Part 1.5: Fix nsIDocument::AsHTMLDocument() r=bz

content/base/public/nsIDocument.h

@@ -2103,7 +2103,7 @@ public:
   already_AddRefed<nsIDOMTouchList>
     CreateTouchList(const mozilla::dom::Sequence<nsRefPtr<nsIDOMTouch> >& aTouches);
 
-  nsHTMLDocument* AsHTMLDocument();
+  virtual nsHTMLDocument* AsHTMLDocument() { return nullptr; }
 
 private:
   uint64_t mWarnedAbout;

content/base/src/nsDocument.cpp

@@ -1906,12 +1906,6 @@ nsDocument::Init()
   return NS_OK;
 }
 
-nsHTMLDocument*
-nsIDocument::AsHTMLDocument()
-{
-  return IsHTML() ? static_cast<nsHTMLDocument*>(this) : nullptr;
-}
-
 void
 nsIDocument::DeleteAllProperties()
 {

content/html/document/src/nsHTMLDocument.h

@@ -255,6 +255,8 @@ public:
     return nsIDocument::GetLocation();
   }
 
+  virtual nsHTMLDocument* AsHTMLDocument() { return this; }
+
 protected:
   nsresult GetBodySize(int32_t* aWidth,
                        int32_t* aHeight);