Rename DesktopEngagement* to DesktopSessionDuration*.

chrome/browser/metrics/desktop_engagement/audible_contents_tracker.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_AUDIBLE_CONTENTS_TRACKER_H_
-#define CHROME_BROWSER_METRICS_DESKTOP_ENGAGEMENT_AUDIBLE_CONTENTS_TRACKER_H_
-
-#include <set>
-
-#include "base/callback.h"
-#include "chrome/browser/ui/browser_list_observer.h"
-#include "chrome/browser/ui/tabs/tab_strip_model_observer.h"
-
-namespace metrics {
-
-// BrowserList / TabStripModelObserver used for tracking audio status.
-class AudibleContentsTracker : public chrome::BrowserListObserver,
-                               public TabStripModelObserver {
- public:
-  // Interface for an observer of the AudibleContentsTracker. The only client
-  // of this class is the DesktopEngagementService, but an observer interface
-  // has been created for ease of testing.
-  class Observer {
-   public:
-    Observer() {}
-    virtual ~Observer() {}
-
-    // Invoked when a first audio source starts playing after a period of no
-    // audio sources.
-    virtual void OnAudioStart() = 0;
-
-    // Invoked when all audio sources stop playing.
-    virtual void OnAudioEnd() = 0;
-
-   private:
-    DISALLOW_COPY_AND_ASSIGN(Observer);
-  };
-
-  // Creates an audible contents tracker that dispatches its messages to the
-  // provided |observer|.
-  explicit AudibleContentsTracker(Observer* observer);
-  ~AudibleContentsTracker() override;
-
- private:
-  // chrome::BrowserListObserver:
-  void OnBrowserAdded(Browser* browser) override;
-  void OnBrowserRemoved(Browser* browser) override;
-
-  // TabStripModelObserver:
-  void TabClosingAt(TabStripModel* model,
-                    content::WebContents* web_contents,
-                    int index) override;
-  void TabChangedAt(content::WebContents* web_contents,
-                    int index,
-                    TabChangeType change_type) override;
-  void TabReplacedAt(TabStripModel* model,
-                     content::WebContents* old_web_contents,
-                     content::WebContents* new_web_contents,
-                     int index) override;
-
-  // Used for managing audible_contents_, and invoking OnAudioStart and
-  // OnAudioEnd callbacks.
-  void AddAudibleWebContents(content::WebContents* web_contents);
-  void RemoveAudibleWebContents(content::WebContents* web_contents);
-
-  Observer* observer_;
-
-  // The set of WebContents that are currently playing audio.
-  std::set<content::WebContents*> audible_contents_;
-
-  DISALLOW_COPY_AND_ASSIGN(AudibleContentsTracker);
-};
-
-}  // namespace metrics
-
-#endif  // CHROME_BROWSER_METRICS_DESKTOP_ENGAGEMENT_AUDIBLE_CONTENTS_TRACKER_H_