Add Startup.SameVersionStartupCount histogram

components/startup_metric_utils/browser/pref_names.h

Index: components/startup_metric_utils/browser/pref_names.h
diff --git a/components/startup_metric_utils/browser/pref_names.h b/components/startup_metric_utils/browser/pref_names.h
new file mode 100644
index 0000000000000000000000000000000000000000..11a97095bfbbed33f69455b7fa462fa9808c8830
--- /dev/null
+++ b/components/startup_metric_utils/browser/pref_names.h
@@ -0,0 +1,21 @@
+// Copyright 2016 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 COMPONENTS_STARTUP_METRIC_UTILS_BROWSER_PREF_NAMES_H_
+#define COMPONENTS_STARTUP_METRIC_UTILS_BROWSER_PREF_NAMES_H_
+
+namespace startup_metric_utils {
+namespace prefs {
+
+// Alphabetical list of preference names specific to the startup_metric_utils
+// component. Keep alphabetized, and document each in the .cc file.
+
+extern const char kLastStartupTimestamp[];
+extern const char kLastStartupVersion[];
+extern const char kSameVersionStartupCount[];
+
+}  // namespace prefs
+}  // namespace startup_metric_utils
+
+#endif  // COMPONENTS_STARTUP_METRIC_UTILS_BROWSER_PREF_NAMES_H_