[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>
 
@@ skipping 89 matching lines @@
                                       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);
 
+  // Record resources loaded by NoStatePrefetch.
+  void RecordResourcePrefetch(Origin origin,
+                              bool is_main_resource,
+                              bool is_no_store);
+
  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.
   bool WithinWindow() const;
@@ skipping 18 matching lines @@
   // start recording events before the first prerender occurs.
   bool seen_any_pageload_;
   bool seen_pageload_started_after_prerender_;
 
   DISALLOW_COPY_AND_ASSIGN(PrerenderHistograms);
 };
 
 }  // namespace prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_HISTOGRAMS_H_