Add some histograms for <a ping> requests.

content/browser/loader/detachable_resource_handler.h

 // Copyright 2013 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 CONTENT_BROWSER_LOADER_DETACHABLE_RESOURCE_HANDLER_H_
 #define CONTENT_BROWSER_LOADER_DETACHABLE_RESOURCE_HANDLER_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
+#include "base/timer/elapsed_timer.h"
 #include "base/timer/timer.h"
 #include "content/browser/loader/resource_handler.h"
 #include "content/public/browser/resource_controller.h"
+#include "net/url_request/url_request_status.h"
 
 namespace net {
 class IOBuffer;
 class URLRequest;
 }  // namespace net
 
 namespace content {
 
 // A ResourceHandler which delegates all calls to the next handler, unless
 // detached. Once detached, it drives the request to completion itself. This is
@@ skipping 47 matching lines @@
                                    bool* defer) OVERRIDE;
   virtual void OnDataDownloaded(int request_id, int bytes_downloaded) OVERRIDE;
 
   // ResourceController implementation:
   virtual void Resume() OVERRIDE;
   virtual void Cancel() OVERRIDE;
   virtual void CancelAndIgnore() OVERRIDE;
   virtual void CancelWithError(int error_code) OVERRIDE;
 
  private:
+  void TimedOut();
+
   scoped_ptr<ResourceHandler> next_handler_;
   scoped_refptr<net::IOBuffer> read_buffer_;
 
   scoped_ptr<base::OneShotTimer<DetachableResourceHandler> > detached_timer_;
   base::TimeDelta cancel_delay_;
 
   bool is_deferred_;
   bool is_finished_;
+  bool timed_out_;
+
+  bool response_started_;
+  base::ElapsedTimer time_since_start_;
+
+  // The status recorded from OnResponseCompleted. Value is
+  // net::URLRequestStatus::IO_PENDING if OnResponseCompleted is never received.
+  net::URLRequestStatus::Status status_;
 
   DISALLOW_COPY_AND_ASSIGN(DetachableResourceHandler);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LOADER_DETACHABLE_RESOURCE_HANDLER_H_