Changes to support using base/feature_list.h from gin/.

base/feature_list.cc

 // Copyright 2015 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 "base/feature_list.h"
 
 #include <stddef.h>
 
 #include <utility>
 #include <vector>
@@ skipping 125 matching lines @@
   return GetInstance()->IsFeatureEnabled(feature);
 }
 
 // static
 std::vector<std::string> FeatureList::SplitFeatureListString(
     const std::string& input) {
   return SplitString(input, ",", TRIM_WHITESPACE, SPLIT_WANT_NONEMPTY);
 }
 
 // static
-void FeatureList::InitializeInstance(const std::string& enable_features,
+bool FeatureList::InitializeInstance(const std::string& enable_features,
                                      const std::string& disable_features) {
   // We want to initialize a new instance here to support command-line features
   // in testing better. For example, we initialize a dummy instance in
   // base/test/test_suite.cc, and override it in content/browser/
   // browser_main_loop.cc.
   // On the other hand, we want to avoid re-initialization from command line.
   // For example, we initialize an instance in chrome/browser/
   // chrome_browser_main.cc and do not override it in content/browser/
   // browser_main_loop.cc.
+  bool instance_existed_before = false;
   if (g_instance) {
     if (g_instance->initialized_from_command_line_)
-      return;
+      return false;
 
     delete g_instance;
     g_instance = nullptr;
+    instance_existed_before = true;
   }
 
   std::unique_ptr<base::FeatureList> feature_list(new base::FeatureList);
   feature_list->InitializeFromCommandLine(enable_features, disable_features);
   base::FeatureList::SetInstance(std::move(feature_list));
+  return !instance_existed_before;
 }
 
 // static
 FeatureList* FeatureList::GetInstance() {
   return g_instance;
 }
 
 // static
 void FeatureList::SetInstance(std::unique_ptr<FeatureList> instance) {
   DCHECK(!g_instance);
@@ skipping 89 matching lines @@
   return it->second == &feature;
 }
 
 FeatureList::OverrideEntry::OverrideEntry(OverrideState overridden_state,
                                           FieldTrial* field_trial)
     : overridden_state(overridden_state),
       field_trial(field_trial),
       overridden_by_field_trial(field_trial != nullptr) {}
 
 }  // namespace base