Make UserActivityDetector a singleton

extensions/shell/browser/shell_desktop_controller.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 "extensions/shell/browser/shell_desktop_controller.h"
 
 #include <algorithm>
 #include <string>
 #include <vector>
 
@@ skipping 258 matching lines @@
   host_->window()->SetLayoutManager(new FillLayout);
 
   cursor_manager_.reset(
       new wm::CursorManager(scoped_ptr<wm::NativeCursorManager>(
           new ShellNativeCursorManager(host_.get()))));
   cursor_manager_->SetDisplay(
       gfx::Screen::GetNativeScreen()->GetPrimaryDisplay());
   cursor_manager_->SetCursor(ui::kCursorPointer);
   aura::client::SetCursorClient(host_->window(), cursor_manager_.get());
 
-  user_activity_detector_.reset(new wm::UserActivityDetector);
   host_->event_processor()->GetRootTarget()->AddPreTargetHandler(
-      user_activity_detector_.get());
+      wm::UserActivityDetector::Get());
 #if defined(OS_CHROMEOS)
-  user_activity_notifier_.reset(
-      new ui::UserActivityPowerManagerNotifier(user_activity_detector_.get()));
+  user_activity_notifier_.reset(new ui::UserActivityPowerManagerNotifier(
+      wm::UserActivityDetector::Get()));
 #endif
 }
 
 void ShellDesktopController::CreateRootWindow() {
   // Set up basic pieces of ui::wm.
   gfx::Size size;
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
   if (command_line->HasSwitch(switches::kAppShellHostWindowBounds)) {
     const std::string size_str =
         command_line->GetSwitchValueASCII(switches::kAppShellHostWindowBounds);
@@ skipping 21 matching lines @@
   host_->AddObserver(this);
 
   // Ensure the X window gets mapped.
   host_->Show();
 }
 
 void ShellDesktopController::DestroyRootWindow() {
   host_->RemoveObserver(this);
   if (input_method_filter_)
     root_window_event_filter_->RemoveHandler(input_method_filter_.get());
-  if (user_activity_detector_) {
-    host_->event_processor()->GetRootTarget()->RemovePreTargetHandler(
-        user_activity_detector_.get());
-  }
+  host_->event_processor()->GetRootTarget()->RemovePreTargetHandler(
+      wm::UserActivityDetector::Get());
   wm::FocusController* focus_controller =
       static_cast<wm::FocusController*>(focus_client_.get());
   if (focus_controller) {
     host_->window()->RemovePreTargetHandler(focus_controller);
     aura::client::SetActivationClient(host_->window(), NULL);
   }
   root_window_event_filter_.reset();
   capture_client_.reset();
   input_method_filter_.reset();
   focus_client_.reset();
   cursor_manager_.reset();
 #if defined(OS_CHROMEOS)
   user_activity_notifier_.reset();
 #endif
-  user_activity_detector_.reset();
   host_.reset();
 }
 
 gfx::Size ShellDesktopController::GetPrimaryDisplaySize() {
 #if defined(OS_CHROMEOS)
   const std::vector<ui::DisplayConfigurator::DisplayState>& displays =
       display_configurator_->cached_displays();
   if (displays.empty())
     return gfx::Size();
   const ui::DisplayMode* mode = displays[0].display->current_mode();
   return mode ? mode->size() : gfx::Size();
 #else
   return gfx::Size();
 #endif
 }
 
 }  // namespace extensions