Avoid blocking while mapping an X11 window

ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h

Index: ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
index 40933bc596479e6cd9e5a73b8fbe066ef83882fe..3096e7d741b67859552e4bc59be7b597e7938b52 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
@@ -278,6 +278,11 @@ class VIEWS_EXPORT DesktopWindowTreeHostX11
   // Is the window mapped to the screen?
   bool window_mapped_;
 
+  // If |wait_for_map_| is true, it means we called MapWindow, but haven't yet
+  // gotten the MapNotify event yet. We use this as part of the calculation for
+  // whether the window is "visible".
+  bool wait_for_map_;

[Tom (Use chromium acct), 2016/09/12 22:45:07]

Since this cl means we don't wait for maps anymore, |wait_for_map_| probably
needs to be renamed.

[dackerman, 2016/09/23 14:12:37]

How about |is_waiting_for_map_|, |expecting_map_notify_|, or
|map_window_called_|? Maybe some combination of these?  In a sense it is
"waiting" for the event to happen, but not blocking the thread. Also, you didn't
mention it, but does it make sense to include this it in the visibility check
like I did?

[Tom (Use chromium acct), 2016/09/23 18:35:48]

It does make sense to add the check for wait_for_map_ in the visibility check
since that way, a window will be IsVisible() right after a Show(), which matches
the current behavior with the blocking.

However, I've changed my mind about this.  We should instead remove both the
wait_for_map_ and wait_for_unmap_ logic and just introduce is_visible_.

is_visible_ will be initialized to false.
It will be set to true where you have "wait_for_map_ = true"
It will be set to false where we currently have "wait_for_unmap = true"
IsVisible() should just return is_visible_
Change the comment on window_mapped_ (line 278) to reflect that it means the
window is mapped w.r.t. the X server.
Add a comment on is_visible_ to reflect that it means the window is visible
w.r.t. Aura.

[dackerman, 2016/09/25 19:45:36]

Done.

+
   // Should we wait for an UnmapNotify before trying to remap the window?
   // If |wait_for_unmap_| is true, we have sent an XUnmapWindow request to the
   // server and have yet to receive an UnmapNotify.