Bug 638241. Part 1: remove useless QI. r=bzbarsky

content/canvas/src/CanvasUtils.cpp

@@ -83,17 +83,14 @@ CanvasUtils::DoDrawImageSecurityCheck(nsHTMLCanvasElement *aCanvasElement,
     if (aPrincipal == nsnull)
         return;
 
-    nsCOMPtr<nsINode> elem = do_QueryInterface(static_cast<nsIDOMHTMLCanvasElement*>(aCanvasElement));
-    if (elem) { // XXXbz How could this actually be null?
     PRBool subsumes;
     nsresult rv =
-            elem->NodePrincipal()->Subsumes(aPrincipal, &subsumes);
+        aCanvasElement->NodePrincipal()->Subsumes(aPrincipal, &subsumes);
 
     if (NS_SUCCEEDED(rv) && subsumes) {
         // This canvas has access to that image anyway
         return;
     }
-    }
 
     aCanvasElement->SetWriteOnly();
 }