Remove duplicate null check of presShell. (Bug 747231, patch 1) r=roc

--HG--
extra : transplant_source : %05I%BFz%3C%95%CB%19%BCV%08Lx%F5G%88%9B%02S9

dom/base/nsDOMWindowUtils.cpp

@@ -334,7 +334,6 @@ nsDOMWindowUtils::SetDisplayPortForElement(float aXPx, float aYPx,
     }
   }
 
-  if (presShell) {
   nsIFrame* rootFrame = presShell->FrameManager()->GetRootFrame();
   if (rootFrame) {
     nsIContent* rootContent =
@@ -364,7 +363,6 @@ nsDOMWindowUtils::SetDisplayPortForElement(float aXPx, float aYPx,
       }
     }
   }
-  }
 
   return NS_OK;
 }