Move Singleton and related structs to namespace base

mojo/message_pump/handle_watcher.cc

Index: mojo/message_pump/handle_watcher.cc
diff --git a/mojo/message_pump/handle_watcher.cc b/mojo/message_pump/handle_watcher.cc
index d02c761109692b257b18d94332c814b9974a87c3..964f1e2d3348d80b1edef376538ce2eac0862639 100644
--- a/mojo/message_pump/handle_watcher.cc
+++ b/mojo/message_pump/handle_watcher.cc
@@ -190,7 +190,7 @@ class WatcherThreadManager {
 
   typedef std::vector<RequestData> Requests;
 
-  friend struct DefaultSingletonTraits<WatcherThreadManager>;
+  friend struct base::DefaultSingletonTraits<WatcherThreadManager>;
 
   WatcherThreadManager();
 
@@ -222,7 +222,7 @@ WatcherThreadManager::~WatcherThreadManager() {
 }
 
 WatcherThreadManager* WatcherThreadManager::GetInstance() {
-  return Singleton<WatcherThreadManager>::get();
+  return base::Singleton<WatcherThreadManager>::get();
 }
 
 WatcherID WatcherThreadManager::StartWatching(