Move Singleton and related structs to namespace base

content/browser/devtools/shared_worker_devtools_manager.h

Index: content/browser/devtools/shared_worker_devtools_manager.h
diff --git a/content/browser/devtools/shared_worker_devtools_manager.h b/content/browser/devtools/shared_worker_devtools_manager.h
index 6a2a828f9bfda49fa3cc65b39519526bd4ae3a5a..22842f53038d24c9791606e5da4bd7c298043190 100644
--- a/content/browser/devtools/shared_worker_devtools_manager.h
+++ b/content/browser/devtools/shared_worker_devtools_manager.h
@@ -42,7 +42,7 @@ class CONTENT_EXPORT SharedWorkerDevToolsManager {
   void RemoveInspectedWorkerData(WorkerId id);
 
  private:
-  friend struct DefaultSingletonTraits<SharedWorkerDevToolsManager>;
+  friend struct base::DefaultSingletonTraits<SharedWorkerDevToolsManager>;
   friend class SharedWorkerDevToolsAgentHost;
   friend class SharedWorkerDevToolsManagerTest;
   FRIEND_TEST_ALL_PREFIXES(SharedWorkerDevToolsManagerTest, BasicTest);