Eliminate PlatformWindowMus::Activate

ui/views/mus/native_widget_mus.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/mus/native_widget_mus.h"
 
 #include "base/macros.h"
 #include "base/thread_task_runner_handle.h"
 #include "components/mus/public/cpp/property_type_converters.h"
 #include "components/mus/public/cpp/window.h"
@@ skipping 778 matching lines @@
     GetWidget()->SetInitialFocus(state);
   }
 }
 
 bool NativeWidgetMus::IsVisible() const {
   // TODO(beng): this should probably be wired thru PlatformWindow.
   return window_ && window_->visible();
 }
 
 void NativeWidgetMus::Activate() {
-  if (window_tree_host_)
-    window_tree_host_->platform_window()->Activate();
+  if (window_)
+    window_->SetFocus();
 }
 
 void NativeWidgetMus::Deactivate() {
   if (IsActive())
     window_->connection()->ClearFocus();
 }
 
 bool NativeWidgetMus::IsActive() const {
   mus::Window* focused =
       window_ ? window_->connection()->GetFocusedWindow() : nullptr;
@@ skipping 310 matching lines @@
     window_tree_host_->Show();
     GetNativeWindow()->Show();
   } else {
     window_tree_host_->Hide();
     GetNativeWindow()->Hide();
   }
   native_widget_delegate_->OnNativeWidgetVisibilityChanged(window->visible());
 }
 
 }  // namespace views