Moves MruWindowTracker into common

ash/wm/mru_window_tracker.h

Index: ash/wm/mru_window_tracker.h
diff --git a/ash/wm/mru_window_tracker.h b/ash/wm/mru_window_tracker.h
deleted file mode 100644
index 3c0fc0a5692f5216bdf1af8296024948bb38687e..0000000000000000000000000000000000000000
--- a/ash/wm/mru_window_tracker.h
+++ /dev/null
@@ -1,68 +0,0 @@
-// Copyright 2013 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_MRU_WINDOW_TRACKER_H_
-#define ASH_WM_MRU_WINDOW_TRACKER_H_
-
-#include <list>
-#include <vector>
-
-#include "ash/ash_export.h"
-#include "ash/common/wm_activation_observer.h"
-#include "ash/common/wm_window_observer.h"
-#include "base/macros.h"
-
-namespace ash {
-
-class WmWindow;
-
-// Maintains a most recently used list of windows. This is used for window
-// cycling using Alt+Tab and overview mode.
-class ASH_EXPORT MruWindowTracker : public WmActivationObserver,
-                                    public WmWindowObserver {
- public:
-  using WindowList = std::vector<WmWindow*>;
-
-  MruWindowTracker();
-  ~MruWindowTracker() override;
-
-  // Returns the set of windows which can be cycled through using the tracked
-  // list of most recently used windows.
-  WindowList BuildMruWindowList() const;
-
-  // This does the same thing as the above, but ignores the system modal dialog
-  // state and hence the returned list could contain more windows if a system
-  // modal dialog window is present.
-  WindowList BuildWindowListIgnoreModal() const;
-
-  // Starts or stops ignoring window activations. If no longer ignoring
-  // activations the currently active window is moved to the front of the
-  // MRU window list. Used by WindowCycleList to avoid adding all cycled
-  // windows to the front of the MRU window list.
-  void SetIgnoreActivations(bool ignore);
-
- private:
-  // Updates the mru_windows_ list to insert/move |active_window| at/to the
-  // front.
-  void SetActiveWindow(WmWindow* active_window);
-
-  // Overridden from WmActivationObserver:
-  void OnWindowActivated(WmWindow* gained_active,
-                         WmWindow* lost_active) override;
-
-  // Overridden from WmWindowObserver:
-  void OnWindowDestroyed(WmWindow* window) override;
-
-  // List of windows that have been activated in containers that we cycle
-  // through, sorted by most recently used.
-  std::list<WmWindow*> mru_windows_;
-
-  bool ignore_window_activations_;
-
-  DISALLOW_COPY_AND_ASSIGN(MruWindowTracker);
-};
-
-}  // namespace ash
-
-#endif  // ASH_WM_MRU_WINDOW_TRACKER_H_