Refactors maximize mode event handling into its own class

ash/mus/bridge/wm_shell_mus.cc

 // 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.
 
 #include "ash/mus/bridge/wm_shell_mus.h"
 
 #include "ash/common/default_accessibility_delegate.h"
 #include "ash/common/display/display_info.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shell_observer.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/system/tray/default_system_tray_delegate.h"
+#include "ash/common/wm/maximize_mode/maximize_mode_event_handler.h"
 #include "ash/common/wm/mru_window_tracker.h"
 #include "ash/common/wm/window_resizer.h"
 #include "ash/common/wm_activation_observer.h"
 #include "ash/common/wm_shell_common.h"
 #include "ash/mus/bridge/wm_root_window_controller_mus.h"
 #include "ash/mus/bridge/wm_window_mus.h"
 #include "ash/mus/container_ids.h"
 #include "ash/mus/drag_window_resizer.h"
 #include "ash/mus/root_window_controller.h"
 #include "base/memory/ptr_util.h"
@@ skipping 200 matching lines @@
   NOTIMPLEMENTED();
 }
 
 std::unique_ptr<WindowResizer> WmShellMus::CreateDragWindowResizer(
     std::unique_ptr<WindowResizer> next_window_resizer,
     wm::WindowState* window_state) {
   return base::WrapUnique(
       new DragWindowResizer(std::move(next_window_resizer), window_state));
 }
 
+std::unique_ptr<wm::MaximizeModeEventHandler>
+WmShellMus::CreateMaximizeModeEventHandler() {
+  // TODO: need support for window manager to get events before client:
+  // http://crbug.com/624157.
+  NOTIMPLEMENTED();
+  return nullptr;
+}
+
 void WmShellMus::OnOverviewModeStarting() {
   FOR_EACH_OBSERVER(ShellObserver, *wm_shell_common_->shell_observers(),
                     OnOverviewModeStarting());
 }
 
 void WmShellMus::OnOverviewModeEnded() {
   FOR_EACH_OBSERVER(ShellObserver, *wm_shell_common_->shell_observers(),
                     OnOverviewModeEnded());
 }
 
@@ skipping 70 matching lines @@
                     OnWindowActivated(gained_active, lost_active));
 }
 
 void WmShellMus::OnWillDestroyClient(::mus::WindowTreeClient* client) {
   DCHECK_EQ(client, client_);
   RemoveClientObserver();
 }
 
 }  // namespace mus
 }  // namespace ash