Only record the execution time during startup.

components/history/core/browser/top_sites_backend.h

 // Copyright (c) 2011 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_HISTORY_CORE_BROWSER_TOP_SITES_BACKEND_H_
 #define COMPONENTS_HISTORY_CORE_BROWSER_TOP_SITES_BACKEND_H_
 
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "components/history/core/browser/history_types.h"
 
 namespace base {
 class CancelableTaskTracker;
 class FilePath;
 class SingleThreadTaskRunner;
 }
 
 namespace history {
 
 class TopSitesDatabase;
 
 // Service used by TopSites to have db interaction happen on the DB thread.  All
 // public methods are invoked on the ui thread and get funneled to the DB
 // thread.
 class TopSitesBackend : public base::RefCountedThreadSafe<TopSitesBackend> {
  public:
+  // TODO(yiyaoliu): Remove the enums and related code when crbug/223430 is
+  // fixed.
+
+  // An enum representing different situations under which function
+  // TopSitesImpl::SetTopSites and TopSitesBackend::UpdateTopSites can be
+  // initiated.
+  // This is needed because a histogram is used to record speed related metrics
+  // when TopSitesImpl::SetTopSites and TopSitesBackend::UpdateTopSites are
+  // initiated from TopSitesImpl::OnGotMostVisitedThumbnails, which usually
+  // happens early and might affect Chrome startup speed.
+  enum CallLocation {
+    // SetTopSites is called when MostVisitedThumbnails is available (function
+    // TopSitesImpl::OnGotMostVisitedThumbnails).
+    CALL_LOCATION_FROM_ON_GOT_MOST_VISITED_THUMBNAILS,
+    // All other situations.
+    CALL_LOCATION_FROM_OTHER_PLACES
+  };
+
+  // An enum representing the histogram recording status used by class
+  // TopSitesImpl and class TopSitesBackend. The purpose is to make sure that
+  // TopSitesImpl and TopSitesBackend records the relevant histograms at most
+  // once during startup.
+  // The initial value will be HISTOGRAM_RECORDING_NOT_YET. TopSitesImpl will
+  // change it to HISTOGRAM_RECORDING_IN_PROGRESS and records a histogram.
+  // TopSitesBackend will only records the value if this enum is
+  // HISTOGRAM_RECORDING_IN_PROGRESS and after that it changes the enum value to
+  // HISTOGRAM_RECORDING_DONE.
+  enum HistogramRecording {
+    HISTOGRAM_RECORDING_NOT_YET,
+    HISTOGRAM_RECORDING_IN_PROGRESS,
+    HISTOGRAM_RECORDING_DONE
+  };
+
+  // Move the histogram recording status to the next step.
+  static void IncraseHistogramRecordingStatus();

[sky, 2015/04/16 16:05:10]

Increase
Why does this need to be public? Doesn't
TopSitesBackend::UpdateTopSitesOnDBThread have enough information to know it can
increase?

+  static HistogramRecording histogram_recorded() { return histogram_recorded_; }
+
   // The boolean parameter indicates if the DB existed on disk or needs to be
   // migrated.
   typedef base::Callback<void(const scoped_refptr<MostVisitedThumbnails>&)>
       GetMostVisitedThumbnailsCallback;
 
   explicit TopSitesBackend(
       const scoped_refptr<base::SingleThreadTaskRunner>& db_task_runner);
 
   void Init(const base::FilePath& path);
 
   // Schedules the db to be shutdown.
   void Shutdown();
 
   // Fetches MostVisitedThumbnails.
   void GetMostVisitedThumbnails(
       const GetMostVisitedThumbnailsCallback& callback,
       base::CancelableTaskTracker* tracker);
 
   // Updates top sites database from the specified delta.
-  void UpdateTopSites(const TopSitesDelta& delta);
+  // TODO(yiyaoliu): Remove the 2nd parameter when crbug/223430 is fixed.
+  void UpdateTopSites(const TopSitesDelta& delta,
+                      const CallLocation location);
 
   // Sets the thumbnail.
   void SetPageThumbnail(const MostVisitedURL& url,
                         int url_rank,
                         const Images& thumbnail);
 
   // Deletes the database and recreates it.
   void ResetDatabase();
 
   // Schedules a request that does nothing on the DB thread, but then notifies
@@ skipping 11 matching lines @@
   void InitDBOnDBThread(const base::FilePath& path);
 
   // Shuts down the db.
   void ShutdownDBOnDBThread();
 
   // Does the work of getting the most visted thumbnails.
   void GetMostVisitedThumbnailsOnDBThread(
       scoped_refptr<MostVisitedThumbnails> thumbnails);
 
   // Updates top sites.
-  void UpdateTopSitesOnDBThread(const TopSitesDelta& delta);
+  // TODO(yiyaoliu): Remove the 2nd parameter when crbug/223430 is fixed.
+  void UpdateTopSitesOnDBThread(const TopSitesDelta& delta,
+                                const CallLocation location);
 
   // Sets the thumbnail.
   void SetPageThumbnailOnDBThread(const MostVisitedURL& url,
                                   int url_rank,
                                   const Images& thumbnail);
 
   // Resets the database.
   void ResetDatabaseOnDBThread(const base::FilePath& file_path);
 
   base::FilePath db_path_;
 
   scoped_ptr<TopSitesDatabase> db_;
   scoped_refptr<base::SingleThreadTaskRunner> db_task_runner_;
 
+  static HistogramRecording histogram_recorded_;
+
   DISALLOW_COPY_AND_ASSIGN(TopSitesBackend);
 };
 
 }  // namespace history
 
 #endif  // COMPONENTS_HISTORY_CORE_BROWSER_TOP_SITES_BACKEND_H_