[subresource_filter] Add debugging trace events around activation

components/subresource_filter/core/browser/subresource_filter_features_test_support.cc

 // Copyright 2016 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.
 
 #include "components/subresource_filter/core/browser/subresource_filter_features_test_support.h"
 
+#include <ostream>
 #include <utility>
 
+#include "base/json/json_writer.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/strings/string_util.h"
+#include "base/trace_event/trace_event_argument.h"
+#include "base/values.h"
 
 namespace subresource_filter {
 namespace testing {
 
 // ScopedSubresourceFilterConfigurator ----------------------------------------
 
 ScopedSubresourceFilterConfigurator::ScopedSubresourceFilterConfigurator(
     scoped_refptr<ConfigurationList> configs_list)
     : original_config_(GetAndSetActivateConfigurations(configs_list)) {}
 
@@ skipping 54 matching lines @@
   }
 
   scoped_configuration_.ResetConfiguration();
   scoped_feature_list_ = base::MakeUnique<base::test::ScopedFeatureList>();
   scoped_feature_list_->InitFromCommandLine(enabled_features,
                                             disabled_features);
 }
 
 ScopedSubresourceFilterFeatureToggle::~ScopedSubresourceFilterFeatureToggle() {}
 
+std::ostream& operator<<(std::ostream& os, const Configuration& config) {
+  std::unique_ptr<base::Value> value = config.ToTracedValue()->ToBaseValue();
+  base::DictionaryValue* dict;
+  value->GetAsDictionary(&dict);
+  std::string json;
+  base::JSONWriter::WriteWithOptions(
+      *dict, base::JSONWriter::OPTIONS_PRETTY_PRINT, &json);
+  return os << json;
+}
+
 }  // namespace testing
 }  // namespace subresource_filter