Reland of Improves focus/activation for aura-mus and DesktopNativeWidgetAura

ui/aura/mus/focus_synchronizer.h

Index: ui/aura/mus/focus_synchronizer.h
diff --git a/ui/aura/mus/focus_synchronizer.h b/ui/aura/mus/focus_synchronizer.h
new file mode 100644
index 0000000000000000000000000000000000000000..db2556d76155f0e1cdb8000f5a0ab6af217f901a
--- /dev/null
+++ b/ui/aura/mus/focus_synchronizer.h
@@ -0,0 +1,72 @@
+// 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.
+
+#ifndef UI_AURA_MUS_FOCUS_SYNCHRONIZER_H_
+#define UI_AURA_MUS_FOCUS_SYNCHRONIZER_H_
+
+#include "base/macros.h"
+#include "ui/aura/client/focus_change_observer.h"
+#include "ui/aura/env_observer.h"
+
+namespace ui {
+namespace mojom {
+class WindowTree;
+}
+}
+
+namespace aura {
+
+class FocusSynchronizerDelegate;
+class WindowMus;
+
+namespace client {
+class FocusClient;
+}
+
+// FocusSynchronizer is resonsible for keeping focus in sync between aura
+// and the mus server.
+class FocusSynchronizer : public client::FocusChangeObserver,
+                          public EnvObserver {
+ public:
+  FocusSynchronizer(FocusSynchronizerDelegate* delegate,
+                    ui::mojom::WindowTree* window_tree);
+  ~FocusSynchronizer() override;
+
+  // Called when the server side wants to change focus to |window|.
+  void SetFocusFromServer(WindowMus* window);
+
+  // Called when the focused window is destroyed.
+  void OnFocusedWindowDestroyed();
+
+  WindowMus* focused_window() { return focused_window_; }
+
+ private:
+  void SetActiveFocusClient(client::FocusClient* focus_client);
+
+  // Called internally to set |focused_window_| and update the server.
+  void SetFocusedWindow(WindowMus* window);
+
+  // Overriden from client::FocusChangeObserver:
+  void OnWindowFocused(Window* gained_focus, Window* lost_focus) override;
+
+  // Overrided from EnvObserver:
+  void OnWindowInitialized(Window* window) override;
+  void OnActiveFocusClientChanged(client::FocusClient* focus_client,
+                                  Window* window) override;
+
+  FocusSynchronizerDelegate* delegate_;
+  ui::mojom::WindowTree* window_tree_;
+
+  client::FocusClient* active_focus_client_ = nullptr;
+
+  bool setting_focus_ = false;
+  WindowMus* window_setting_focus_to_ = nullptr;
+  WindowMus* focused_window_ = nullptr;
+
+  DISALLOW_COPY_AND_ASSIGN(FocusSynchronizer);
+};
+
+}  // namespace aura
+
+#endif  // UI_AURA_MUS_FOCUS_SYNCHRONIZER_H_