aura-mus: Implement Deactivate().

ui/views/mus/desktop_window_tree_host_mus.cc

 // Copyright 2016 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/desktop_window_tree_host_mus.h"
 
 #include "base/memory/ptr_util.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/client/cursor_client.h"
 #include "ui/aura/client/drag_drop_client.h"
@@ skipping 435 matching lines @@
   aura::Env::GetInstance()->SetActiveFocusClient(
       aura::client::GetFocusClient(window()), window());
   if (is_active_) {
     window()->Focus();
     if (window()->GetProperty(aura::client::kDrawAttentionKey))
       window()->SetProperty(aura::client::kDrawAttentionKey, false);
   }
 }
 
 void DesktopWindowTreeHostMus::Deactivate() {
-  // TODO: Deactivate() means focus next window, that needs to go to mus.
-  // http://crbug.com/663618.
-  NOTIMPLEMENTED();
+  if (is_active_)
+    ClearFocus();
 }
 
 bool DesktopWindowTreeHostMus::IsActive() const {
   return is_active_;
 }
 
 void DesktopWindowTreeHostMus::Maximize() {
   window()->SetProperty(aura::client::kShowStateKey, ui::SHOW_STATE_MAXIMIZED);
 }
 void DesktopWindowTreeHostMus::Minimize() {
@@ skipping 201 matching lines @@
   if (window == this->window()) {
     is_active_ = true;
     desktop_native_widget_aura_->HandleActivationChanged(true);
   } else if (is_active_) {
     is_active_ = false;
     desktop_native_widget_aura_->HandleActivationChanged(false);
   }
 }
 
 }  // namespace views