Fix for crash when closing main window while print dialog is open (checked in for Frank Tang). b=35896, sr=vidur, r=adamlock

dom/src/base/nsGlobalWindow.cpp

@@ -2593,6 +2593,9 @@ NS_IMETHODIMP GlobalWindowImpl::GetPrivateRoot(nsIDOMWindowInternal ** aParent)
 
   nsCOMPtr<nsIScriptGlobalObject> parentTop = do_QueryInterface(parent);
   nsCOMPtr<nsIDocShell> docShell;
+  NS_ASSERTION(parentTop, "cannot get parentTop");
+  if(parentTop == nsnull)
+    return NS_ERROR_FAILURE;
   parentTop->GetDocShell(getter_AddRefs(docShell));
   nsCOMPtr<nsIChromeEventHandler> chromeEventHandler;
   docShell->GetChromeEventHandler(getter_AddRefs(chromeEventHandler));

layout/base/nsPresShell.cpp

@@ -2125,6 +2125,9 @@ static void CheckForFocus(nsIDocument* aDocument)
   nsCOMPtr<nsIDOMWindowInternal> rootWindow;
   nsCOMPtr<nsPIDOMWindow> ourWindow = do_QueryInterface(globalObject);
   ourWindow->GetPrivateRoot(getter_AddRefs(rootWindow));
+  NS_ASSERTION(rootWindow , "cannot get rootWindow");
+  if(nsnull == rootWindow)
+    return;
   nsCOMPtr<nsIDOMDocument> rootDocument;
   rootWindow->GetDocument(getter_AddRefs(rootDocument));
 

layout/html/base/src/nsPresShell.cpp

@@ -2125,6 +2125,9 @@ static void CheckForFocus(nsIDocument* aDocument)
   nsCOMPtr<nsIDOMWindowInternal> rootWindow;
   nsCOMPtr<nsPIDOMWindow> ourWindow = do_QueryInterface(globalObject);
   ourWindow->GetPrivateRoot(getter_AddRefs(rootWindow));
+  NS_ASSERTION(rootWindow , "cannot get rootWindow");
+  if(nsnull == rootWindow)
+    return;
   nsCOMPtr<nsIDOMDocument> rootDocument;
   rootWindow->GetDocument(getter_AddRefs(rootDocument));