276692 get nsIGdkPixbufImage using GI(nsIImage) followed by

QI(nsIGdkPixbufImage)
r=bryner sr=dbaron

browser/components/shell/src/nsGNOMEShellService.cpp

@@ -344,7 +344,11 @@ nsGNOMEShellService::SetShouldCheckDefaultBrowser(PRBool aShouldCheck)
 static nsresult
 WriteImage(const nsCString& aPath, gfxIImageFrame* aImage)
 {
-  nsCOMPtr<nsIGdkPixbufImage> pixImg(do_GetInterface(aImage));
+  nsCOMPtr<nsIImage> img(do_GetInterface(aImage));
+  if (!img)
+      return NS_ERROR_NOT_AVAILABLE;
+
+  nsCOMPtr<nsIGdkPixbufImage> pixImg(do_QueryInterface(img));
   if (!pixImg)
       return NS_ERROR_NOT_AVAILABLE;
 

widget/src/gtk2/nsWindow.cpp

@@ -819,7 +819,11 @@ nsWindow::SetCursor(imgIContainer* aCursor)
     if (!frame)
         return NS_ERROR_NOT_AVAILABLE;
 
-    nsCOMPtr<nsIGdkPixbufImage> pixImg(do_GetInterface(frame));
+    nsCOMPtr<nsIImage> img(do_GetInterface(frame));
+    if (!img)
+        return NS_ERROR_NOT_AVAILABLE;
+
+    nsCOMPtr<nsIGdkPixbufImage> pixImg(do_QueryInterface(img));
     if (!pixImg)
         return NS_ERROR_NOT_AVAILABLE;