Avoid blocking while mapping an X11 window

ui/events/platform/x11/x11_event_source.h

Index: ui/events/platform/x11/x11_event_source.h
diff --git a/ui/events/platform/x11/x11_event_source.h b/ui/events/platform/x11/x11_event_source.h
index bd925027856034e64c30dee5786a9a07486f7a15..6f63c49fd900821b3a3b91f9ff2bdd5fb53a6b0b 100644
--- a/ui/events/platform/x11/x11_event_source.h
+++ b/ui/events/platform/x11/x11_event_source.h
@@ -67,8 +67,6 @@ class EVENTS_EXPORT X11EventSource {
   // functions which require a mapped window.
   void BlockUntilWindowMapped(XID window);

[Tom (Use chromium acct), 2016/09/26 17:26:04]

This should be done in the future, but I just want to document it here for now. 
There are only 2 remaining places that calls BlockUntilWindowMapped, and those
are in x11_window_base.cc and x11_whole_screen_move_loop.cc.  The former is just
like this case, and should be removed.  The other is done on an
override-redirect window, so we don't need to block for a map.

This means we can remove BlockUntilWindowMapped and BlockOnWindowStructureEvent.

 
-  void BlockUntilWindowUnmapped(XID window);
-
   XDisplay* display() { return display_; }
 
   // Returns the timestamp of the event currently being dispatched.  Falls back