Bug 1115481 - Move 'window' variable declaration in the #ifdef it's used from. r=karlt

testing/tools/screenshot/gdk-screenshot.cpp

@@ -127,10 +127,10 @@ int main(int argc, char** argv)
   }
 #endif
 
-  GdkWindow* window = gdk_get_default_root_window();
   GdkPixbuf* screenshot = nullptr;
 // TODO GTK3
 #if (MOZ_WIDGET_GTK == 2)
+  GdkWindow* window = gdk_get_default_root_window();
   screenshot = gdk_pixbuf_get_from_drawable(nullptr, window, nullptr,
                                             0, 0, 0, 0,
                                             gdk_screen_width(),