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

content/browser/renderer_host/media/media_track_lifetime_metrics_host.h

Index: content/browser/renderer_host/media/media_track_lifetime_metrics_host.h
diff --git a/content/browser/renderer_host/media/media_track_lifetime_metrics_host.h b/content/browser/renderer_host/media/media_track_lifetime_metrics_host.h
new file mode 100644
index 0000000000000000000000000000000000000000..4c89d12d813940c7774cd6791ed5201e19d9355f
--- /dev/null
+++ b/content/browser/renderer_host/media/media_track_lifetime_metrics_host.h
@@ -0,0 +1,67 @@
+// 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_TRACK_LIFETIME_METRICS_HOST_H_
+#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_TRACK_LIFETIME_METRICS_HOST_H_
+
+#include <map>
+#include <string>
+
+#include "base/time/time.h"
+#include "content/public/browser/browser_message_filter.h"
+#include "content/public/browser/render_process_host_observer.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 MediaTrackLifetimeMetricsHost
+    : public BrowserMessageFilter,
+      public RenderProcessHostObserver {
+ public:
+  explicit MediaTrackLifetimeMetricsHost(RenderProcessHost* owner);
+
+ protected:
+  virtual ~MediaTrackLifetimeMetricsHost();
+
+  // BrowserMessageFilter override.
+  virtual bool OnMessageReceived(const IPC::Message& message,
+                                 bool* message_was_ok) OVERRIDE;
+
+  // RenderProcessHostObserver override.
+  virtual void RenderProcessExited(RenderProcessHost* host,
+                                   base::ProcessHandle handle,
+                                   base::TerminationStatus status,
+                                   int exit_code) OVERRIDE;
+
+ private:
+  void OnAddTrack(const std::string& id, bool is_audio);
+  void OnRemoveTrack(const std::string& id);
+
+  void ReportDuration(bool is_audio, base::TimeTicks start_time);
+
+  // Keys are 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<std::string, IsAudioPlusTimestamp> TrackMap;
+  TrackMap tracks_;
+
+  // Non-owning pointer.
+  RenderProcessHost* owner_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_MEDIA_TRACK_LIFETIME_METRICS_HOST_H_