Putting histogram names of tracked prefs in tracked_preference_histogram_name file.

components/user_prefs/tracked/tracked_preference_histogram_names.cc

+// 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.
+
+#include "components/user_prefs/tracked/tracked_preference_histogram_names.h"
+
+namespace user_prefs {
+namespace tracked {
+
+// Tracked pref histogram names.
+const char kTrackedPrefHistogramUnchanged[] =
+    "Settings.TrackedPreferenceUnchanged";
+const char kTrackedPrefHistogramCleared[] = "Settings.TrackedPreferenceCleared";
+const char kTrackedPrefHistogramMigratedLegacyDeviceId[] =
+    "Settings.TrackedPreferenceMigratedLegacyDeviceId";
+const char kTrackedPrefHistogramChanged[] = "Settings.TrackedPreferenceChanged";
+const char kTrackedPrefHistogramInitialized[] =
+    "Settings.TrackedPreferenceInitialized";
+const char kTrackedPrefHistogramTrustedInitialized[] =
+    "Settings.TrackedPreferenceTrustedInitialized";
+const char kTrackedPrefHistogramNullInitialized[] =
+    "Settings.TrackedPreferenceNullInitialized";
+const char kTrackedPrefHistogramWantedReset[] =
+    "Settings.TrackedPreferenceWantedReset";
+const char kTrackedPrefHistogramReset[] = "Settings.TrackedPreferenceReset";
+const char kTrackedSplitPrefHistogramChanged[] =
+    "Settings.TrackedSplitPreferenceChanged.";
+
+}  // namespace tracked
+}  // namespace user_prefs