Bug 1400757 - Add telemetry to MediaRecorder and TrackEncoder to track basic usage. r=francois,pehrsons

Add telemetry to collect the following:
- Number of times a MediaRecorder is started during a session
- Duration of media recordings
- How often we're timing out init of audio and video track encoders

MozReview-Commit-ID: 9Pc2oKNCH1M

--HG--
extra : rebase_source : 16414a5ffa95413458d36295e5508df4c16e6fa9

dom/media/MediaRecorder.cpp

@@ -1199,6 +1199,8 @@ MediaRecorder::Start(const Optional<int32_t>& aTimeSlice, ErrorResult& aResult)
   mSessions.AppendElement();
   mSessions.LastElement() = new Session(this, timeSlice);
   mSessions.LastElement()->Start();
+  mStartTime = TimeStamp::Now();
+  Telemetry::ScalarAdd(Telemetry::ScalarID::MEDIARECORDER_RECORDING_COUNT, 1);
 }
 
 void
@@ -1574,6 +1576,12 @@ MediaRecorder::StopForSessionDestruction()
   mState = RecordingState::Inactive;
   MOZ_ASSERT(mSessions.Length() > 0);
   mSessions.LastElement()->Stop();
+  // This is a coarse calculation and does not reflect the duration of the
+  // final recording for reasons such as pauses. However it allows us an idea
+  // of how long people are running their recorders for.
+  TimeDuration timeDelta = TimeStamp::Now() - mStartTime;
+  Telemetry::Accumulate(Telemetry::MEDIA_RECORDER_RECORDING_DURATION,
+                        timeDelta.ToSeconds());
 }
 
 void

dom/media/MediaRecorder.h

@@ -168,6 +168,8 @@ protected:
   uint32_t mVideoBitsPerSecond;
   uint32_t mBitsPerSecond;
 
+  TimeStamp mStartTime;
+
   // DOMExceptions that are created early and possibly thrown in NotifyError.
   // Creating them early allows us to capture the JS stack for which cannot be
   // done at the time the error event is fired.

dom/media/encoder/TrackEncoder.cpp

@@ -229,6 +229,8 @@ AudioTrackEncoder::TryInit(const AudioSegment& aSegment, StreamTime aDuration)
                AUDIO_INIT_FAILED_DURATION,
                DEFAULT_CHANNELS));
     nsresult rv = Init(DEFAULT_CHANNELS, mTrackRate);
+    Telemetry::Accumulate(
+      Telemetry::MEDIA_RECORDER_TRACK_ENCODER_INIT_TIMEOUT_TYPE, 0);
     if (NS_FAILED(rv)) {
       TRACK_LOG(LogLevel::Error,
                 ("[AudioTrackEncoder %p]: Default-channel-init failed.", this));
@@ -522,6 +524,8 @@ VideoTrackEncoder::Init(const VideoSegment& aSegment, StreamTime aDuration)
     TRACK_LOG(LogLevel::Warning,
       ("[VideoTrackEncoder %p]: No successful init for %ds.",
        this, VIDEO_INIT_FAILED_DURATION));
+    Telemetry::Accumulate(
+      Telemetry::MEDIA_RECORDER_TRACK_ENCODER_INIT_TIMEOUT_TYPE, 1);
     OnError();
     return;
   }

toolkit/components/telemetry/Histograms.json

@@ -9268,6 +9268,25 @@
     "n_values": 8,
     "description": "Type of call: (Bitmask) Audio = 1, Video = 2, DataChannels = 4"
   },
+  "MEDIA_RECORDER_RECORDING_DURATION": {
+    "record_in_processes": ["main", "content"],
+    "alert_emails": ["bvandyk@mozilla.com"],
+    "expires_in_version": "60",
+    "kind": "exponential",
+    "high": 3600,
+    "n_buckets": 100,
+    "bug_numbers": [1400757],
+    "description": "The length of time (in seconds) that a recording lasted. Recorded when a recorder stops"
+  },
+  "MEDIA_RECORDER_TRACK_ENCODER_INIT_TIMEOUT_TYPE": {
+    "record_in_processes": ["main", "content"],
+    "alert_emails": ["bvandyk@mozilla.com"],
+    "expires_in_version": "60",
+    "kind": "enumerated",
+    "n_values": 4,
+    "bug_numbers": [1400757],
+    "description": "Records the type of timeout that happened while attempting to init the encoder. Audio = 0, Video = 1. Recorded immediately following a timeout"
+  },
   "DEVTOOLS_ENTRY_POINT": {
     "record_in_processes": ["main"],
     "bug_numbers": [1378863],

toolkit/components/telemetry/Scalars.yaml

@@ -633,6 +633,21 @@ webrtc.nicer:
       - 'main'
       - 'content'
 
+mediarecorder:
+  recording_count:
+    bug_numbers:
+      - 1400757
+    description: >
+      The number of times a MediaRecorder has been started. Recorded when a MediaRecorder starts
+    expires: "60"
+    kind: uint
+    notification_emails:
+      - bvandyk@mozilla.com
+    release_channel_collection: opt-in
+    record_in_processes:
+      - main
+      - content
+
 # The following section contains content process base counters.
 dom.contentprocess:
   troubled_due_to_memory: