Initialize data reduction proxy bypass stats on IO thread

components/data_reduction_proxy/core/browser/data_reduction_proxy_bypass_stats.h

Index: components/data_reduction_proxy/core/browser/data_reduction_proxy_bypass_stats.h
diff --git a/components/data_reduction_proxy/core/browser/data_reduction_proxy_bypass_stats.h b/components/data_reduction_proxy/core/browser/data_reduction_proxy_bypass_stats.h
index be08aa55afd7884b196464a220273d8c3e736b22..22674e9f1aa7b29ac26a1b542f5a21c8f03cf9e0 100644
--- a/components/data_reduction_proxy/core/browser/data_reduction_proxy_bypass_stats.h
+++ b/components/data_reduction_proxy/core/browser/data_reduction_proxy_bypass_stats.h
@@ -10,6 +10,7 @@
 #include "base/callback.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
+#include "base/threading/thread_checker.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/network_change_notifier.h"
@@ -55,6 +56,9 @@ class DataReductionProxyBypassStats
 
   ~DataReductionProxyBypassStats() override;
 
+  // Performs initialization on the IO thread.
+  void InitializeOnIOThread();
+
   // Callback intended to be called from |DataReductionProxyNetworkDelegate|
   // when a request completes. This method is used to gather bypass stats.
   void OnUrlRequestCompleted(const net::URLRequest* request,
@@ -154,6 +158,8 @@ class DataReductionProxyBypassStats
   // Whether or not the data reduction proxy is unavailable.
   bool unavailable_;
 
+  base::ThreadChecker thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(DataReductionProxyBypassStats);
 };