chromeos: fix focus for mushrome

ash/mus/window_manager.cc

Index: ash/mus/window_manager.cc
diff --git a/ash/mus/window_manager.cc b/ash/mus/window_manager.cc
index 4372ddf6dd5e413c437144bcaf66f482961fcb28..fc0a1ab756aa0c523e1bbbb689a2cd2f115155ca 100644
--- a/ash/mus/window_manager.cc
+++ b/ash/mus/window_manager.cc
@@ -249,13 +249,6 @@ void WindowManager::CreateAndRegisterRootWindowController(
   std::unique_ptr<RootWindowController> root_window_controller(
       new RootWindowController(nullptr, window_tree_host.release()));
   root_window_controller->Init(root_window_type);
-  // TODO: To avoid lots of IPC AddActivationParent() should take an array.
-  // http://crbug.com/682048.
-  aura::Window* root_window = root_window_controller->GetRootWindow();
-  for (size_t i = 0; i < kNumActivatableShellWindowIds; ++i) {
-    window_manager_client_->AddActivationParent(
-        root_window->GetChildById(kActivatableShellWindowIds[i]));
-  }
   root_window_controllers_.insert(std::move(root_window_controller));
 }