Add an adapter layer (WMHelper) between exo and ash.

components/exo/wm_helper.h

Index: components/exo/wm_helper.h
diff --git a/components/exo/wm_helper.h b/components/exo/wm_helper.h
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+++ b/components/exo/wm_helper.h
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+// 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 COMPONENTS_EXO_WM_HELPER_H_
+#define COMPONENTS_EXO_WM_HELPER_H_
+
+#include "ash/common/shell_observer.h"
+#include "base/macros.h"
+#include "base/observer_list.h"
+#include "ui/aura/client/cursor_client_observer.h"
+#include "ui/aura/client/focus_change_observer.h"
+#include "ui/wm/public/activation_change_observer.h"
+
+namespace ash {
+class DisplayInfo;
+}
+
+namespace aura {
+class Window;
+}
+
+namespace ui {
+class EventHandler;
+}
+
+namespace base {
+template <typename T>
+struct DefaultSingletonTraits;
+}
+
+namespace exo {
+
+// A helper class for accessing WindowManager related features.
+class WMHelper : public aura::client::ActivationChangeObserver,
+                 public aura::client::FocusChangeObserver,
+                 public aura::client::CursorClientObserver,
+                 public ash::ShellObserver {
+ public:
+  class ActivationObserver {
+   public:
+    virtual void OnWindowActivated(aura::Window* gained_active,
+                                   aura::Window* lost_active) = 0;
+
+   protected:
+    virtual ~ActivationObserver() {}
+  };
+
+  class FocusObserver {
+   public:
+    virtual void OnWindowFocused(aura::Window* gained_focus,
+                                 aura::Window* lost_focus) = 0;
+
+   protected:
+    virtual ~FocusObserver() {}
+  };
+
+  class CursorObserver {
+   public:
+    virtual void OnCursorVisibilityChanged(bool is_visible) {}
+    virtual void OnCursorSetChanged(ui::CursorSetType cursor_set) {}
+
+   protected:
+    virtual ~CursorObserver() {}
+  };
+
+  class MaximizeModeObserver {
+   public:
+    virtual void OnMaximizeModeStarted() = 0;
+    virtual void OnMaximizeModeEnded() = 0;
+
+   protected:
+    virtual ~MaximizeModeObserver() {}
+  };
+
+  static WMHelper* GetInstance();
+
+  const ash::DisplayInfo& GetDisplayInfo(int64_t display_id) const;
+  static aura::Window* GetContainer(int container_id);
+
+  aura::Window* GetActiveWindow() const;
+  void AddActivationObserver(ActivationObserver* observer);
+  void RemoveActivationObserver(ActivationObserver* observer);
+
+  aura::Window* GetFocusedWindow() const;
+  void AddFocusObserver(FocusObserver* observer);
+  void RemoveFocusObserver(FocusObserver* observer);
+
+  ui::CursorSetType GetCursorSet() const;
+  void AddCursorObserver(CursorObserver* observer);
+  void RemoveCursorObserver(CursorObserver* observer);
+
+  void AddPreTargetHandler(ui::EventHandler* handler);
+  void PrependPreTargetHandler(ui::EventHandler* handler);
+  void RemovePreTargetHandler(ui::EventHandler* handler);
+
+  void AddPostTargetHandler(ui::EventHandler* handler);
+  void RemovePostTargetHandler(ui::EventHandler* handler);
+
+  bool IsMaximizeModeWindowManagerEnabled() const;
+  void AddMaximizeModeObserver(MaximizeModeObserver* observer);
+  void RemoveMaximizeModeObserver(MaximizeModeObserver* observer);
+
+ private:
+  WMHelper();
+  ~WMHelper() override;
+
+  friend struct base::DefaultSingletonTraits<WMHelper>;
+
+  // aura::client::ActivationChangeObserver overrides:

[reveman, 2016/08/16 13:14:14]

nit: "// Overridden from aura::client::ActivationChangeObserver:" to be
consistent with the rest of the exo/ code

[Peng, 2016/08/16 14:01:29]

Done.

+  void OnWindowActivated(
+      aura::client::ActivationChangeObserver::ActivationReason reason,
+      aura::Window* gained_active,
+      aura::Window* lost_active) override;
+
+  // aura::client::FocusChangeObserver overrides:

[reveman, 2016/08/16 13:14:14]

nit: // Overridden from.. 

[Peng, 2016/08/16 14:01:29]

Done.

+  void OnWindowFocused(aura::Window* gained_focus,
+                       aura::Window* lost_focus) override;
+
+  // aura::client::CursorClientObserver overrides:

[reveman, 2016/08/16 13:14:14]

nit: // Overridden from..

[Peng, 2016/08/16 14:01:29]

Done.

+  void OnCursorVisibilityChanged(bool is_visible) override;
+  void OnCursorSetChanged(ui::CursorSetType cursor_set) override;
+
+  // ash::ShellObserver overrides:

[reveman, 2016/08/16 13:14:14]

nit: // Overridden from..

[Peng, 2016/08/16 14:01:29]

Done.

+  void OnMaximizeModeStarted() override;
+  void OnMaximizeModeEnded() override;
+
+  base::ObserverList<ActivationObserver> activation_observers_;
+  base::ObserverList<FocusObserver> focus_observers_;
+  base::ObserverList<CursorObserver> cursor_observers_;
+  base::ObserverList<MaximizeModeObserver> maximize_mode_observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(WMHelper);
+};
+
+}  // namespace exo
+
+#endif  // COMPONENTS_EXO_WM_HELPER_H_