Adds UMA metrics for renderer uptime

chrome/browser/metrics/renderer_uptime_tracker.h

+// Copyright 2017 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_RENDERER_UPTIME_TRACKER_H_
+#define CHROME_BROWSER_METRICS_RENDERER_UPTIME_TRACKER_H_
+
+#include <map>
+
+#include "base/time/time.h"
+
+// ChromeStabilityMetricsProvider gathers and logs Chrome-specific stability-
+// related metrics.
+class RendererUptimeTracker {
+ public:
+  // Creates the |RendererUptimeTracker| instance and initializes the
+  // observers that notify to it.
+  static void Initialize();
+
+  // Returns true if the |RendererUptimeTracker| instance has been
+  // created.
+  static bool IsInitialized();
+
+  // Returns the |RendererUptimeTracker| instance.
+  static RendererUptimeTracker* Get();
+
+  void OnRendererStarted(int pid);
+  void OnRendererTerminated(int pid);
+  void OnLoadInMainFrame(int pid);
+
+ protected:
+  RendererUptimeTracker();
+  ~RendererUptimeTracker();
+
+  struct RendererInfo {
+    base::TimeTicks launched_at_;
+    int num_loads_;
+    int num_loads_in_main_frame_;
+  };
+
+ private:
+  std::map<int, RendererInfo> info_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(RendererUptimeTracker);
+};
+
+#endif  // CHROME_BROWSER_METRICS_RENDERER_UPTIME_TRACKER_H_