Histogram appcache task queue and run times.

webkit/appcache/appcache_histograms.h

Index: webkit/appcache/appcache_histograms.h
===================================================================
--- webkit/appcache/appcache_histograms.h	(revision 110360)
+++ webkit/appcache/appcache_histograms.h	(working copy)
@@ -8,6 +8,10 @@
 
 #include "base/basictypes.h"
 
+namespace base {
+class TimeDelta;
+}
+
 namespace appcache {
 
 class AppCacheHistograms {
@@ -25,6 +29,10 @@
   };
   static void CountCheckResponseResult(CheckResponseResultType result);
 
+  static void AddTaskQueueTimeSample(const base::TimeDelta& duration);
+  static void AddTaskRunTimeSample(const base::TimeDelta& duration);
+  static void AddTaskCompletionTimeSample(const base::TimeDelta& duration);
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(AppCacheHistograms);
 };