mus: Disregard windows that explicitly set can_accept_events to be false when sending events.

services/ui/ws/window_tree.h

Index: services/ui/ws/window_tree.h
diff --git a/services/ui/ws/window_tree.h b/services/ui/ws/window_tree.h
index 6555ff338d78c45b8b5c69b8bf89338b6f8360e0..78b01d28ff68a83638c177cd1ad9593777d6eed0 100644
--- a/services/ui/ws/window_tree.h
+++ b/services/ui/ws/window_tree.h
@@ -167,6 +167,8 @@ class WindowTree : public mojom::WindowTree,
   bool SetWindowVisibility(const ClientWindowId& window_id, bool visible);
   bool SetWindowOpacity(const ClientWindowId& window_id, float opacity);
   bool SetFocus(const ClientWindowId& window_id);
+  void SetCanAcceptEvents(Id transport_window_id,

[msw, 2016/07/12 22:07:23]

nit: reorder to match decl and keep overrides together.
(maybe add a separate synchronous wrapper if needed?)

[riajiang, 2016/07/13 00:01:46]

Moved to after SetCanFocus and added a function in test::WindowTreeTestApi to
access this (now private)

+                          bool can_accept_events) override;
   bool Embed(const ClientWindowId& window_id,
              mojom::WindowTreeClientPtr client,
              uint32_t flags);