Rename DesktopEngagement* to DesktopSessionDuration*.

chrome/browser/metrics/desktop_engagement/desktop_engagement_service.h

-// 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.
-
-#ifndef CHROME_BROWSER_METRICS_DESKTOP_ENGAGEMENT_DESKTOP_ENGAGEMENT_SERVICE_H_
-#define CHROME_BROWSER_METRICS_DESKTOP_ENGAGEMENT_DESKTOP_ENGAGEMENT_SERVICE_H_
-
-#include "base/macros.h"
-#include "base/memory/weak_ptr.h"
-#include "base/time/time.h"
-#include "base/timer/timer.h"
-#include "chrome/browser/metrics/desktop_engagement/audible_contents_tracker.h"
-#include "chrome/browser/metrics/desktop_engagement/chrome_visibility_observer.h"
-
-namespace metrics {
-
-// Class for tracking and recording user engagement based on browser visibility,
-// audio and user interaction.
-class DesktopEngagementService : public AudibleContentsTracker::Observer {
- public:
-  // Creates the |DesktopEngagementService| instance and initializes the
-  // observes that notify to it.
-  static void Initialize();
-
-  // Returns true if the |DesktopEngagementService| instance has been created.
-  static bool IsInitialized();
-
-  // Returns the |DesktopEngagementService| instance.
-  static DesktopEngagementService* Get();
-
-  // Called when user interaction with the browser is caught.
-  void OnUserEvent();
-
-  // Called when visibility of the browser changes.
-  void OnVisibilityChanged(bool visible);
-
-  bool is_visible() const { return is_visible_; }
-  bool in_session() const { return in_session_; }
-  bool is_audio_playing() const { return is_audio_playing_; }
-
-  void SetInactivityTimeoutForTesting(int seconds) {
-    inactivity_timeout_ = base::TimeDelta::FromSeconds(seconds);
-  }
-
- protected:
-  DesktopEngagementService();
-  ~DesktopEngagementService() override;
-
-  // AudibleContentsTracker::Observer
-  void OnAudioStart() override;
-  void OnAudioEnd() override;
-
-  // Decides whether session should be ended. Called when timer for inactivity
-  // timeout was fired. Overridden by tests.
-  virtual void OnTimerFired();
-
- private:
-  // Starts timer based on |inactivity_timeout_|.
-  void StartTimer(base::TimeDelta duration);
-
-  // Marks the start of the session.
-  void StartSession();
-
-  // Ends the session and saves session information into histograms.
-  void EndSession();
-
-  // Sets |inactivity_timeout_| based on variation params.
-  void InitInactivityTimeout();
-
-  // Used for marking start if the session.
-  base::TimeTicks session_start_;
-
-  // Used for marking last user interaction.
-  base::TimeTicks last_user_event_;
-
-  // Used for marking current state of the user engagement.
-  bool is_visible_ = false;
-  bool in_session_ = false;
-  bool is_audio_playing_ = false;
-  bool is_first_session_ = true;
-
-  // Timeout for waiting for user interaction.
-  base::TimeDelta inactivity_timeout_;
-
-  base::OneShotTimer timer_;
-
-  ChromeVisibilityObserver visibility_observer_;
-  AudibleContentsTracker audio_tracker_;
-
-  base::WeakPtrFactory<DesktopEngagementService> weak_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(DesktopEngagementService);
-};
-
-}  // namespace metrics
-
-#endif  // CHROME_BROWSER_METRICS_DESKTOP_ENGAGEMENT_DESKTOP_ENGAGEMENT_SERVICE_H_