Initialize data reduction proxy bypass stats on IO thread

components/data_reduction_proxy/core/browser/data_reduction_proxy_interceptor.h

Index: components/data_reduction_proxy/core/browser/data_reduction_proxy_interceptor.h
diff --git a/components/data_reduction_proxy/core/browser/data_reduction_proxy_interceptor.h b/components/data_reduction_proxy/core/browser/data_reduction_proxy_interceptor.h
index 365d4a2c9e18618517a063917253299e5e5d83fc..2c4af95ba0f21138232873e1be2e55dae06448ac 100644
--- a/components/data_reduction_proxy/core/browser/data_reduction_proxy_interceptor.h
+++ b/components/data_reduction_proxy/core/browser/data_reduction_proxy_interceptor.h
@@ -8,6 +8,7 @@
 #include <memory>
 
 #include "base/macros.h"
+#include "base/threading/thread_checker.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h"
 #include "net/url_request/url_request_interceptor.h"
 
@@ -85,6 +86,8 @@ class DataReductionProxyInterceptor : public net::URLRequestInterceptor {
   // these cases.
   std::unique_ptr<DataReductionProxyBypassProtocol> bypass_protocol_;
 
+  base::ThreadChecker thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(DataReductionProxyInterceptor);
 };