Move ObserverList to base namespace.

extensions/browser/api/extensions_api_client.cc

Index: extensions/browser/api/extensions_api_client.cc
diff --git a/extensions/browser/api/extensions_api_client.cc b/extensions/browser/api/extensions_api_client.cc
index 36ac1fd690f9e763745d03294ae7d5371063b815..adf9090ba77c7a68ddc1b1f4b407e772f54213d0 100644
--- a/extensions/browser/api/extensions_api_client.cc
+++ b/extensions/browser/api/extensions_api_client.cc
@@ -28,8 +28,10 @@ ExtensionsAPIClient* ExtensionsAPIClient::Get() { return g_instance; }
 void ExtensionsAPIClient::AddAdditionalValueStoreCaches(
     content::BrowserContext* context,
     const scoped_refptr<SettingsStorageFactory>& factory,
-    const scoped_refptr<ObserverListThreadSafe<SettingsObserver> >& observers,
-    std::map<settings_namespace::Namespace, ValueStoreCache*>* caches) {}
+    const scoped_refptr<base::ObserverListThreadSafe<SettingsObserver>>&
+        observers,
+    std::map<settings_namespace::Namespace, ValueStoreCache*>* caches) {
+}
 
 AppViewGuestDelegate* ExtensionsAPIClient::CreateAppViewGuestDelegate() const {
   return NULL;