Only record the execution time during startup.

components/history/core/browser/top_sites_backend.h

Index: components/history/core/browser/top_sites_backend.h
diff --git a/components/history/core/browser/top_sites_backend.h b/components/history/core/browser/top_sites_backend.h
index d3c054b81032026a27077b0837323c028fba7eaf..de612e09033e5f22b52dd7462c39ed44a3a6786e 100644
--- a/components/history/core/browser/top_sites_backend.h
+++ b/components/history/core/browser/top_sites_backend.h
@@ -45,7 +45,10 @@ class TopSitesBackend : public base::RefCountedThreadSafe<TopSitesBackend> {
       base::CancelableTaskTracker* tracker);
 
   // Updates top sites database from the specified delta.
-  void UpdateTopSites(const TopSitesDelta& delta);
+  // The bool param is used for knowing weather this function is called during
+  // startup or not, thus histogram value could be recorded accordingly.
+  // TODO(yiyaoliu): Remove this when crbug/223430 is fixed.
+  void UpdateTopSites(const TopSitesDelta& delta, bool startup);
 
   // Sets the thumbnail.
   void SetPageThumbnail(const MostVisitedURL& url,
@@ -77,7 +80,10 @@ class TopSitesBackend : public base::RefCountedThreadSafe<TopSitesBackend> {
       scoped_refptr<MostVisitedThumbnails> thumbnails);
 
   // Updates top sites.
-  void UpdateTopSitesOnDBThread(const TopSitesDelta& delta);
+  // The bool param is used for knowing weather this function is called during
+  // startup or not, thus histogram value could be recorded accordingly.
+  // TODO(yiyaoliu): Remove this when crbug/223430 is fixed.
+  void UpdateTopSitesOnDBThread(const TopSitesDelta& delta, bool startup);
 
   // Sets the thumbnail.
   void SetPageThumbnailOnDBThread(const MostVisitedURL& url,