Log the freshness of the Variations seed in a histogram.

chrome/common/pref_names.h

 // Copyright (c) 2012 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.
 
 // Constants for the names of various preferences, for easier changing.
 
 #ifndef CHROME_COMMON_PREF_NAMES_H_
 #define CHROME_COMMON_PREF_NAMES_H_
 
 #include <stddef.h>
@@ skipping 427 matching lines @@
 extern const char kMetricsClientIDTimestamp[];
 extern const char kMetricsReportingEnabled[];
 extern const char kMetricsInitialLogsXml[];
 extern const char kMetricsInitialLogsProto[];
 extern const char kMetricsOngoingLogsXml[];
 extern const char kMetricsOngoingLogsProto[];
 
 extern const char kBookmarkPromptEnabled[];
 extern const char kBookmarkPromptImpressionCount[];
 
+extern const char kVariationsLastFetchTime[];
 extern const char kVariationsSeed[];
 extern const char kVariationsSeedDate[];
 
 extern const char kProfileLastUsed[];
 extern const char kProfilesLastActive[];
 extern const char kProfilesNumCreated[];
 extern const char kProfileInfoCache[];
 extern const char kProfileCreatedByVersion[];
 
 extern const char kProfileMetrics[];
@@ skipping 399 matching lines @@
 extern const char kRLZDisabled[];
 #endif
 
 #if defined(ENABLE_APP_LIST)
 extern const char kAppListProfile[];
 #endif
 
 }  // namespace prefs
 
 #endif  // CHROME_COMMON_PREF_NAMES_H_