Adds WmShell::RecordTaskSwitchMetric()

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 <utility>
 
 #include "ash/common/display/display_info.h"
 #include "ash/common/keyboard/keyboard_ui.h"
@@ skipping 220 matching lines @@
 }
 
 std::vector<WmWindow*> WmShellMus::GetAllRootWindows() {
   std::vector<WmWindow*> wm_windows(root_window_controllers_.size());
   for (size_t i = 0; i < root_window_controllers_.size(); ++i)
     wm_windows[i] = root_window_controllers_[i]->GetWindow();
   return wm_windows;
 }
 
 void WmShellMus::RecordUserMetricsAction(UserMetricsAction action) {
+  // TODO: http://crbug.com/616581.
   NOTIMPLEMENTED();
 }
 
+void WmShellMus::RecordTaskSwitchMetric(TaskSwitchSource source) {
+  // TODO: http://crbug.com/616581.
+  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<WindowCycleEventFilter>
 WmShellMus::CreateWindowCycleEventFilter() {
   // TODO: implement me, http://crbug.com/629191.
@@ skipping 85 matching lines @@
                     OnWindowActivated(gained_active, lost_active));
 }
 
 void WmShellMus::OnDidDestroyClient(::ui::WindowTreeClient* client) {
   DCHECK_EQ(client, client_);
   RemoveClientObserver();
 }
 
 }  // namespace mus
 }  // namespace ash