Flag mouse messages received when cursor is hidden.

ui/events/event_constants.h

Index: ui/events/event_constants.h
diff --git a/ui/events/event_constants.h b/ui/events/event_constants.h
index c7736622783d2335da227a73f470beeaa3012a38..f59520b241817dad417a26b28381f1336fc69592 100644
--- a/ui/events/event_constants.h
+++ b/ui/events/event_constants.h
@@ -138,6 +138,9 @@ enum MouseEventFlags {
                                      // touch accessibility mode.
   EF_DIRECT_INPUT = 1 << 20,         // Mouse event coming from direct,
                                      // on-screen input.
+  EF_CURSOR_HIDDEN = 1 << 21,        // Mouse event fired when mouse cursor is
+                                     // not visible. Avoid visible screen
+                                     // changes. (Windows only.)
 };
 
 // Result of dispatching an event.