Add metrics to track the duration of tracks received over a PeerConnection.

content/browser/renderer_host/media/media_stream_track_metrics_host.h

Index: content/browser/renderer_host/media/media_stream_track_metrics_host.h
diff --git a/content/browser/renderer_host/media/media_stream_track_metrics_host.h b/content/browser/renderer_host/media/media_stream_track_metrics_host.h
new file mode 100644
index 0000000000000000000000000000000000000000..a80830eeaeb916f486d7db7e282ebdfc322f6ce0
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+++ b/content/browser/renderer_host/media/media_stream_track_metrics_host.h
@@ -0,0 +1,56 @@
+// 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.
+
+#ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_STREAM_TRACK_METRICS_HOST_H_
+#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_STREAM_TRACK_METRICS_HOST_H_
+
+#include <map>
+#include <string>
+
+#include "base/time/time.h"
+#include "content/public/browser/browser_message_filter.h"
+
+namespace content {
+
+// Responsible for logging metrics about audio and video track
+// lifetimes. These are based on messages from the renderer that are
+// sent when tracks are created and destroyed. Unfortunately we can't
+// reliably log the lifetime metric in the renderer because that
+// process may be destroyed at any time by the fast shutdown path (see
+// RenderProcessHost::FastShutdownIfPossible).
+//
+// There is one instance of this class per render process.
+//
+// If the renderer process goes away without sending messages that
+// tracks were removed, this class instead infers that the tracks were
+// removed.
+class MediaStreamTrackMetricsHost
+    : public BrowserMessageFilter {
+ public:
+  explicit MediaStreamTrackMetricsHost();
+
+ protected:
+  virtual ~MediaStreamTrackMetricsHost();
+
+  // BrowserMessageFilter override.
+  virtual bool OnMessageReceived(const IPC::Message& message,
+                                 bool* message_was_ok) OVERRIDE;
+
+ private:
+  void OnAddTrack(uint64 id, bool is_audio, bool is_remote);
+  void OnRemoveTrack(uint64 id);
+
+  void ReportDuration(bool is_audio, base::TimeTicks start_time);
+
+  // Keys are unique (per renderer) track IDs, values are pairs: A
+  // boolean indicating whether the track is an audio track, and a
+  // timestamp from when the track was created.
+  typedef std::pair<bool, base::TimeTicks> IsAudioPlusTimestamp;
+  typedef std::map<uint64, IsAudioPlusTimestamp> TrackMap;
+  TrackMap tracks_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_STREAM_TRACK_METRICS_HOST_H_