Bug 744699 - Call setDisplayPort on the correct presShell. r=roc

dom/base/nsDOMWindowUtils.cpp

@@ -311,6 +311,10 @@ nsDOMWindowUtils::SetDisplayPortForElement(float aXPx, float aYPx,
     return NS_ERROR_INVALID_ARG;
   }
 
+  if (content->GetCurrentDoc() != presShell->GetDocument()) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
   nsRect lastDisplayPort;
   if (nsLayoutUtils::GetDisplayPort(content, &lastDisplayPort) &&
       displayport.IsEqualInterior(lastDisplayPort)) {

mobile/android/chrome/content/browser.js

@@ -1710,6 +1710,7 @@ Tab.prototype = {
 
     // finally, we set the display port, taking care to convert everything into the CSS-pixel
     // coordinate space, because that is what the function accepts.
+    cwu = this.browser.contentWindow.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);
     cwu.setDisplayPortForElement((aDisplayPort.left / resolution) - (aViewportX / zoom),
                                  (aDisplayPort.top / resolution) - (aViewportY / zoom),
                                  (aDisplayPort.right - aDisplayPort.left) / resolution,