Revert of Split Screen mode implementation

athena/wm/mru_window_tracker.cc

-// Copyright 2014 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 "athena/wm/mru_window_tracker.h"
-
-#include "ui/aura/window.h"
-
-namespace athena {
-
-MruWindowTracker::MruWindowTracker(aura::Window* container)
-    : container_(container) {
-  container->AddObserver(this);
-}
-
-MruWindowTracker::~MruWindowTracker() {
-  if (container_)
-    container_->RemoveObserver(this);
-}
-
-aura::Window::Windows MruWindowTracker::GetWindowList() const {
-  return aura::Window::Windows(mru_windows_.begin(), mru_windows_.end());
-}
-
-void MruWindowTracker::MoveToFront(aura::Window* window) {
-  DCHECK(window);
-  CHECK_EQ(container_, window->parent());
-  std::list<aura::Window*>::iterator it =
-      std::find(mru_windows_.begin(), mru_windows_.end(), window);
-  DCHECK(it != mru_windows_.end());
-  mru_windows_.erase(it);
-  mru_windows_.push_back(window);
-}
-
-// Overridden from WindowObserver:
-void MruWindowTracker::OnWillRemoveWindow(aura::Window* window) {
-  std::list<aura::Window*>::iterator it =
-      std::find(mru_windows_.begin(), mru_windows_.end(), window);
-  if (it == mru_windows_.end()) {
-    // All normal windows should be tracked in mru_windows_
-    DCHECK_NE(window->type(), ui::wm::WINDOW_TYPE_NORMAL);
-    return;
-  }
-  mru_windows_.erase(it);
-}
-
-void MruWindowTracker::OnWindowAdded(aura::Window* new_window) {
-  // We are only interested in ordering normal windows.
-  if (new_window->type() == ui::wm::WINDOW_TYPE_NORMAL)
-    mru_windows_.push_back(new_window);
-}
-
-}  // namespace athena