Make UserActivityDetector a singleton

ui/wm/core/user_activity_detector.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 "ui/wm/core/user_activity_detector.h"
 
 #include "base/format_macros.h"
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "ui/events/event.h"
 #include "ui/wm/core/user_activity_observer.h"
 
 namespace wm {
 
 namespace {
 
+UserActivityDetector* g_instance = nullptr;
+
 // Returns a string describing |event|.
 std::string GetEventDebugString(const ui::Event* event) {
   std::string details = base::StringPrintf(
       "type=%d name=%s flags=%d time=%" PRId64,
       event->type(), event->name().c_str(), event->flags(),
       event->time_stamp().InMilliseconds());
 
   if (event->IsKeyEvent()) {
     details += base::StringPrintf(" key_code=%d",
         static_cast<const ui::KeyEvent*>(event)->key_code());
@@ skipping 10 matching lines @@
 }  // namespace
 
 const int UserActivityDetector::kNotifyIntervalMs = 200;
 
 // Too low and mouse events generated at the tail end of reconfiguration
 // will be reported as user activity and turn the screen back on; too high
 // and we'll ignore legitimate activity.
 const int UserActivityDetector::kDisplayPowerChangeIgnoreMouseMs = 1000;
 
 UserActivityDetector::UserActivityDetector() {
+  CHECK(!g_instance);
+  g_instance = this;
 }
 
 UserActivityDetector::~UserActivityDetector() {
+  g_instance = nullptr;
+}
+
+// static
+UserActivityDetector* UserActivityDetector::Get() {
+  return g_instance;
 }
 
 bool UserActivityDetector::HasObserver(UserActivityObserver* observer) const {
   return observers_.HasObserver(observer);
 }
 
 void UserActivityDetector::AddObserver(UserActivityObserver* observer) {
   observers_.AddObserver(observer);
 }
 
@@ skipping 43 matching lines @@
       (now - last_observer_notification_time_).InMillisecondsF() >=
       kNotifyIntervalMs) {
     if (VLOG_IS_ON(1))
       VLOG(1) << "Reporting user activity: " << GetEventDebugString(event);
     FOR_EACH_OBSERVER(UserActivityObserver, observers_, OnUserActivity(event));
     last_observer_notification_time_ = now;
   }
 }
 
 }  // namespace wm