Decouple Metrics Initialization from IO Thread Initialization

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>
 
 #include <map>
 #include <memory>
 #include <set>
 #include <string>
 #include <unordered_set>
 #include <vector>
 
 #include "base/compiler_specific.h"
+#include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/strings/string_piece.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "chrome/browser/net/chrome_network_delegate.h"
 #include "chrome/common/features.h"
 #include "components/metrics/data_use_tracker.h"
 #include "components/prefs/pref_member.h"
@@ skipping 203 matching lines @@
   // visited sites on about:net-internals/#dns and about:dns pages.  Must be
   // called on the IO thread. If |host_filter| is not null, only hosts matched
   // by it are deleted from the cache.
   void ClearHostCache(
       const base::Callback<bool(const std::string&)>& host_filter);
 
   const net::HttpNetworkSession::Params& NetworkSessionParams() const;
 
   base::TimeTicks creation_time() const;
 
+  // Initializes the callback for updating data use prefs.
+  void InitMetricsDataUseForwarder();
+
   // Returns the callback for updating data use prefs.
   const metrics::UpdateUsagePrefCallbackType& GetMetricsDataUseForwarder();
 
   // Registers the |observer| for new STH notifications.
   void RegisterSTHObserver(net::ct::STHObserver* observer);
 
   // Un-registers the |observer|.
   void UnregisterSTHObserver(net::ct::STHObserver* observer);
 
   // Returns true if the indicated proxy resolution features are
@@ skipping 145 matching lines @@
 
   // True if HTTP/0.9 is allowed on non-default ports by policy.
   bool http_09_on_non_default_ports_enabled_;
 
   const base::TimeTicks creation_time_;
 
   // Callback for updating data use prefs which needs to be initialized on UI
   // thread and passed to |DataUseNetworkDelegate|.
   metrics::UpdateUsagePrefCallbackType metrics_data_use_forwarder_;
 
+#if DCHECK_IS_ON()
+  // True if |metrics_data_use_forwarder_| has been set.
+  bool metrics_data_use_forwarder_set_ = false;
+#endif
+
   base::WeakPtrFactory<IOThread> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(IOThread);
 };
 
 #endif  // CHROME_BROWSER_IO_THREAD_H_