Support a ui::test::EventGenerator constructed with a single argument on Mac

ui/events/test/event_generator.h

Index: ui/events/test/event_generator.h
diff --git a/ui/events/test/event_generator.h b/ui/events/test/event_generator.h
index 77452980cd23f94145779f9b1d300c5640de586a..46f1569dcea675b184c8e6116897e6a5d9889480 100644
--- a/ui/events/test/event_generator.h
+++ b/ui/events/test/event_generator.h
@@ -122,8 +122,7 @@ class EventGenerator {
                  const gfx::Point& initial_location);
 
   // Creates an EventGenerator with the mouse/touch location centered over
-  // |window|. This is currently the only constructor that works on Mac, since
-  // a specific window is required (and there is no root window).
+  // |window|.
   EventGenerator(gfx::NativeWindow root_window, gfx::NativeWindow window);
 
   virtual ~EventGenerator();