[NoStatePrefetch] Add UMA histogram to count prefetch requests

chrome/browser/prerender/prerender_histograms.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.
 
 #ifndef CHROME_BROWSER_PRERENDER_PRERENDER_HISTOGRAMS_H_
 #define CHROME_BROWSER_PRERENDER_PRERENDER_HISTOGRAMS_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <string>
 
 #include "base/macros.h"
+#include "base/threading/thread_checker.h"
 #include "base/time/time.h"
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/prerender/prerender_final_status.h"
 #include "chrome/browser/prerender/prerender_origin.h"
 #include "url/gurl.h"
 
 namespace prerender {
 
 // Navigation type for histograms.
 enum NavigationType {
@@ skipping 74 matching lines @@
   // Record the time since a page was recently visited.
   void RecordTimeSinceLastRecentVisit(Origin origin,
                                       base::TimeDelta time) const;
 
   // Record the bytes in the prerender, whether it was used or not, and the
   // total number of bytes fetched for this profile since the last call to
   // RecordBytes.
   void RecordNetworkBytes(Origin origin,
                           bool used,
                           int64_t prerender_bytes,
-                          int64_t profile_bytes);
+                          int64_t profile_bytes) const;
+
+  // Record resources loaded by NoStatePrefetch.
+  void RecordResourcePrefetch(Origin origin,
+                              bool is_main_resource,
+                              bool is_no_store) const;
 
  private:
   base::TimeTicks GetCurrentTimeTicks() const;
 
   // Returns the time elapsed since the last prerender happened.
   base::TimeDelta GetTimeSinceLastPrerender() const;
 
   // Returns whether the PrerenderManager is currently within the prerender
   // window - effectively, up to 30 seconds after a prerender tag has been
   // observed.
@@ skipping 13 matching lines @@
   // This is used to record perceived PLT's for a certain amount of time
   // from the point that we last saw a <link rel=prerender> tag.
   base::TimeTicks last_prerender_seen_time_;
 
   // Indicates whether we have recorded page load events after the most
   // recent prerender.  These must be initialized to true, so that we don't
   // start recording events before the first prerender occurs.
   bool seen_any_pageload_;
   bool seen_pageload_started_after_prerender_;
 
+  base::ThreadChecker thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(PrerenderHistograms);
 };
 
 }  // namespace prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_HISTOGRAMS_H_