Aura desktop: Really implement DesktopActivationClient::OnWillFocusWindow().

ui/aura/desktop/desktop_activation_client.cc

Index: ui/aura/desktop/desktop_activation_client.cc
diff --git a/ui/aura/desktop/desktop_activation_client.cc b/ui/aura/desktop/desktop_activation_client.cc
index 38e0e4635179111d27747bee0c182c3b1566af41..183a0ee7184139e047956c3119cd1bb6cf36593d 100644
--- a/ui/aura/desktop/desktop_activation_client.cc
+++ b/ui/aura/desktop/desktop_activation_client.cc
@@ -66,8 +66,7 @@ aura::Window* DesktopActivationClient::GetActiveWindow() {
 
 bool DesktopActivationClient::OnWillFocusWindow(Window* window,
                                                 const Event* event) {
-  // TODO(erg): Is this OK? Logic is much more nuanced in ash.
-  return true;
+  return CanActivateWindow(window);
 }
 
 void DesktopActivationClient::OnWindowFocused(aura::Window* window) {