Adding synthetic field trial for DataReductionProxyEnabled

components/data_reduction_proxy/browser/data_reduction_proxy_settings.cc

Index: components/data_reduction_proxy/browser/data_reduction_proxy_settings.cc
diff --git a/components/data_reduction_proxy/browser/data_reduction_proxy_settings.cc b/components/data_reduction_proxy/browser/data_reduction_proxy_settings.cc
index 3f4f0ea1a3d4aa08e601a1dbb7db60c991e6d44b..9fbd3a5a2402bb62a16db374bf18710140696315 100644
--- a/components/data_reduction_proxy/browser/data_reduction_proxy_settings.cc
+++ b/components/data_reduction_proxy/browser/data_reduction_proxy_settings.cc
@@ -131,6 +131,7 @@ void DataReductionProxySettings::InitDataReductionProxySettings(
   url_request_context_getter_ = url_request_context_getter;
   InitPrefMembers();
   RecordDataReductionInit();
+
   // Disable the proxy if it is not allowed to be used.
   if (!params_->allowed())
     return;
@@ -153,6 +154,12 @@ void DataReductionProxySettings::InitDataReductionProxySettings(
   SetProxyConfigurator(configurator.Pass());
 }
 
+void DataReductionProxySettings::SetOnDataReductionEnabledCallback(
+    const base::Callback<void(bool)>& on_data_reduction_proxy_enabled) {
+  on_data_reduction_proxy_enabled_ = on_data_reduction_proxy_enabled;
+  on_data_reduction_proxy_enabled_.Run(IsDataReductionProxyEnabled());
+}
+
 void DataReductionProxySettings::SetProxyConfigurator(
     scoped_ptr<DataReductionProxyConfigurator> configurator) {
   DCHECK(configurator);
@@ -358,6 +365,8 @@ void DataReductionProxySettings::OnIPAddressChanged() {
 
 void DataReductionProxySettings::OnProxyEnabledPrefChange() {
   DCHECK(thread_checker_.CalledOnValidThread());
+  if (!on_data_reduction_proxy_enabled_.is_null())
+    on_data_reduction_proxy_enabled_.Run(IsDataReductionProxyEnabled());
   if (!params_->allowed())
     return;
   MaybeActivateDataReductionProxy(false);