Set focusibility correctly when initializing a window in mus+ash.

ui/aura/mus/window_manager_delegate.h

Index: ui/aura/mus/window_manager_delegate.h
diff --git a/ui/aura/mus/window_manager_delegate.h b/ui/aura/mus/window_manager_delegate.h
index 87f907a3575eb9a6e60b6443245675f768cece77..4f5f137d92bc6734e467a0f6500dbca64e2eb100 100644
--- a/ui/aura/mus/window_manager_delegate.h
+++ b/ui/aura/mus/window_manager_delegate.h
@@ -94,6 +94,10 @@ class AURA_EXPORT WindowManagerDelegate {
       const std::string& name,
       std::unique_ptr<std::vector<uint8_t>>* new_data) = 0;
 
+  // A client requested to change focusibility of |window|. We currently assume
+  // this always succeeds.
+  virtual void OnWmSetCanFocus(Window* window, bool can_focus) = 0;
+
   // A client has requested a new top level window. The delegate should create
   // and parent the window appropriately and return it. |properties| is the
   // supplied properties from the client requesting the new window. The