Implement UMA log throttling for cellular connections

chrome/browser/io_thread.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_IO_THREAD_H_
 #define CHROME_BROWSER_IO_THREAD_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 580 matching lines @@
       system_url_request_context_getter_;
 
   // True if SPDY is disabled by policy.
   bool is_spdy_disabled_by_policy_;
 
   // True if QUIC is allowed by policy.
   bool is_quic_allowed_by_policy_;
 
   const base::TimeTicks creation_time_;
 
+  // Callback for updating data use prefs which needs to be initialized on UI
+  // thread and passed to |ChromeNetworkDelegate|.
+  metrics::UpdateUsagePrefCallbackType metrics_data_use_forwarder_;
+
   base::WeakPtrFactory<IOThread> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(IOThread);
 };
 
 #endif  // CHROME_BROWSER_IO_THREAD_H_