[WIP] ash/extensions: Add experimental extension support for window-management in ash.

ash/wm/window_manager_extension.h

Index: ash/wm/window_manager_extension.h
diff --git a/ash/wm/window_manager_extension.h b/ash/wm/window_manager_extension.h
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+// Copyright (c) 2012 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 ASH_WM_WINDOW_MANAGER_EXTENSION_H_
+#define ASH_WM_WINDOW_MANAGER_EXTENSION_H_
+
+#include <vector>
+
+#include "ash/ash_export.h"
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "ui/aura/client/activation_change_observer.h"
+#include "ui/aura/env_observer.h"
+#include "ui/aura/window_observer.h"
+
+namespace ash {
+
+class WindowManagerExtensionDelegate {
+ public:
+  virtual ~WindowManagerExtensionDelegate() {}
+
+  virtual void OnWindowCreated(const aura::Window* window) = 0;
+
+  virtual void OnWindowClosed(const aura::Window* window) = 0;
+
+  virtual void OnWindowHidden(const aura::Window* window) = 0;
+
+  virtual void OnWindowShown(const aura::Window* window) = 0;
+
+  virtual void OnActiveWindowChanged(const aura::Window* window) = 0;
+};
+
+namespace internal {
+
+class WindowManagerExtension : public aura::EnvObserver,
+                               public aura::WindowObserver,
+                               public aura::client::ActivationChangeObserver {
+ public:
+  WindowManagerExtension();
+  virtual ~WindowManagerExtension();
+
+  void set_delegate(WindowManagerExtensionDelegate* delegate) {
+    delegate_ = delegate;
+  }
+
+ private:
+  // Overridden from aura::EnvObserver:
+  virtual void OnWindowInitialized(aura::Window* window) OVERRIDE;
+
+  // Overridden from aura::WindowObserver:
+  virtual void OnWindowVisibilityChanged(aura::Window* window,
+                                         bool visible) OVERRIDE;
+  virtual void OnWindowDestroyed(aura::Window* window) OVERRIDE;
+
+  // Overridden from aura::client::ActivationChangeObserver:
+  virtual void OnWindowActivated(aura::Window* active,
+                                 aura::Window* old_active) OVERRIDE;
+
+  std::vector<aura::Window*> windows_;
+  WindowManagerExtensionDelegate* delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(WindowManagerExtension);
+};
+
+}  // namespace internal
+}  // namespace ash
+
+#endif  // ASH_WM_WINDOW_MANAGER_EXTENSION_H_