Start recording background video watch time.

media/blink/watch_time_reporter.h

Index: media/blink/watch_time_reporter.h
diff --git a/media/blink/watch_time_reporter.h b/media/blink/watch_time_reporter.h
index 81ea7bd6200d4b9022057c46acd072f40f6b03fb..8290bdc1b04807003620dbae5eb903040d40a69d 100644
--- a/media/blink/watch_time_reporter.h
+++ b/media/blink/watch_time_reporter.h
@@ -21,16 +21,21 @@ namespace media {
 // playbacks as well as audio+video playbacks of sufficient size.
 //
 // Watch time for our purposes is defined as the amount of elapsed media time
-// for audio only or audio+video media. A minimum of 7 seconds of unmuted,
-// foreground (where this is video) media must be watched to start watch time
-// monitoring. Watch time is checked every 5 seconds from then on and reported
-// to multiple buckets: All, MSE, SRC, EME, AC, and battery.
+// for audio only or audio+video media. A minimum of 7 seconds of unmuted media
+// must be watched to start watch time monitoring. Watch time is checked every 5
+// seconds from then on and reported to multiple buckets: All, MSE, SRC, EME,
+// AC, and battery.
 //
 // Any one of paused, hidden (where this is video), or muted is sufficient to
 // stop watch time metric reports. Each of these has a hysteresis where if the
 // state change is undone within 5 seconds, the watch time will be counted as
 // uninterrupted.
 //
+// If the media is audio+video, foreground watch time is logged to the normal
+// AudioVideo bucket, while background watch time goes to the specific
+// AudioVideo.Background bucket. As with other events, there is hysteresis on
+// change between the foreground and background.
+//
 // Power events (on/off battery power) have a similar hysteresis, but unlike
 // the aforementioned properties, will not stop metric collection.
 //
@@ -68,7 +73,8 @@ class MEDIA_BLINK_EXPORT WatchTimeReporter : base::PowerObserver {
 
   // These methods are used to ensure that watch time is only reported for
   // media that is actually playing. They should be called whenever the media
-  // starts or stops playing for any reason.
+  // starts or stops playing for any reason. If the media is audio+video and
+  // currently hidden, OnPlaying() will start background watch time reporting.
   void OnPlaying();
   void OnPaused();
 
@@ -87,7 +93,8 @@ class MEDIA_BLINK_EXPORT WatchTimeReporter : base::PowerObserver {
 
   // These methods are used to ensure that watch time is only reported for
   // videos that are actually visible to the user. They should be called when
-  // the video is shown or hidden respectively.
+  // the video is shown or hidden respectively. OnHidden() will start background
+  // watch time reporting if the media is audio+video.
   //
   // TODO(dalecurtis): At present, this is only called when the entire content
   // window goes into the foreground or background respectively; i.e. it does
@@ -96,9 +103,34 @@ class MEDIA_BLINK_EXPORT WatchTimeReporter : base::PowerObserver {
   void OnShown();
   void OnHidden();
 
+  // Setup the reporting interval to be immediate to avoid spinning real time
+  // within the unit test.
+  void set_reporting_interval_for_testing() {
+    reporting_interval_ = base::TimeDelta();
+  }
+
+  void set_is_on_battery_power_for_testing(bool on_battery_power) {
+    is_on_battery_power_ = on_battery_power;
+  }
+
+  void OnPowerStateChangeForTesting(bool on_battery_power) {
+    OnPowerStateChange(on_battery_power);
+  }
+
  private:
   friend class WatchTimeReporterTest;
 
+  // Internal constructor for marking background status.
+  WatchTimeReporter(bool has_audio,
+                    bool has_video,
+                    bool is_mse,
+                    bool is_encrypted,
+                    bool is_embedded_media_experience_enabled,
+                    scoped_refptr<MediaLog> media_log,
+                    const gfx::Size& initial_video_size,
+                    const GetMediaTimeCB& get_media_time_cb,
+                    bool is_background);
+
   // base::PowerObserver implementation.
   //
   // We only observe power source changes. We don't need to observe suspend and
@@ -121,6 +153,7 @@ class MEDIA_BLINK_EXPORT WatchTimeReporter : base::PowerObserver {
   scoped_refptr<MediaLog> media_log_;
   const gfx::Size initial_video_size_;
   const GetMediaTimeCB get_media_time_cb_;
+  const bool is_background_;
 
   // The amount of time between each UpdateWatchTime(); this is the frequency by
   // which the watch times are updated. In the event of a process crash or kill
@@ -137,6 +170,7 @@ class MEDIA_BLINK_EXPORT WatchTimeReporter : base::PowerObserver {
 
   // The last media timestamp seen by UpdateWatchTime().
   base::TimeDelta last_media_timestamp_ = kNoTimestamp;
+  base::TimeDelta last_media_power_timestamp_ = kNoTimestamp;
 
   // The starting and ending timestamps used for reporting watch time.
   base::TimeDelta start_timestamp_;
@@ -147,6 +181,10 @@ class MEDIA_BLINK_EXPORT WatchTimeReporter : base::PowerObserver {
   base::TimeDelta start_timestamp_for_power_;
   base::TimeDelta end_timestamp_for_power_ = kNoTimestamp;
 
+  // Special case reporter for handling background video watch time. Configured
+  // as an audio only WatchTimeReporter with |is_background_| set to true.
+  std::unique_ptr<WatchTimeReporter> background_reporter_;
+
   DISALLOW_COPY_AND_ASSIGN(WatchTimeReporter);
 };