Upstream UmaSessionStats.

chrome/browser/android/metrics/uma_session_stats.h

Index: chrome/browser/android/metrics/uma_session_stats.h
diff --git a/chrome/browser/android/metrics/uma_session_stats.h b/chrome/browser/android/metrics/uma_session_stats.h
new file mode 100644
index 0000000000000000000000000000000000000000..173d342bf8098efabfdee6ac3dac1f1dd6587390
--- /dev/null
+++ b/chrome/browser/android/metrics/uma_session_stats.h
@@ -0,0 +1,45 @@
+// Copyright 2015 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_ANDROID_METRICS_UMA_SESSION_STATS_H_
+#define CHROME_BROWSER_ANDROID_METRICS_UMA_SESSION_STATS_H_
+
+#include <jni.h>
+#include <string>
+
+#include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
+
+class UserActionRateCounter;
+
+// The native part of java UmaSessionStats class.
+class UmaSessionStats {
+ public:
+  UmaSessionStats();
+
+  void UmaResumeSession(JNIEnv* env, jobject obj);
+  void UmaEndSession(JNIEnv* env, jobject obj);
+
+  static void RegisterSyntheticFieldTrialWithNameHash(
+      uint32_t trial_name_hash,
+      const std::string& group_name);
+
+  static void RegisterSyntheticFieldTrial(
+      const std::string& trial_name,
+      const std::string& group_name);
+
+ private:
+  ~UmaSessionStats();
+
+  // Start of the current session, used for UMA.
+  base::TimeTicks session_start_time_;
+  int active_session_count_;
+
+  DISALLOW_COPY_AND_ASSIGN(UmaSessionStats);
+};
+
+// Registers the native methods through jni
+bool RegisterUmaSessionStats(JNIEnv* env);
+
+#endif  // CHROME_BROWSER_ANDROID_METRICS_UMA_SESSION_STATS_H_