Move MessageLoop to base namespace.

base/message_loop.h

Index: base/message_loop.h
diff --git a/base/message_loop.h b/base/message_loop.h
index 13bf621205be2bde5bf51db59bd6d559cc67b7e9..0de51ab51789886aa42d677454702f832ce02acf 100644
--- a/base/message_loop.h
+++ b/base/message_loop.h
@@ -42,13 +42,13 @@
 #endif
 
 namespace base {
+
 class HistogramBase;
 class RunLoop;
 class ThreadTaskRunnerHandle;
 #if defined(OS_ANDROID)
 class MessagePumpForUI;
 #endif
-}  // namespace base
 
 // A MessageLoop is used to process events for a particular thread.  There is
 // at most one MessageLoop instance per thread.
@@ -705,4 +705,12 @@ class BASE_EXPORT MessageLoopForIO : public MessageLoop {
 COMPILE_ASSERT(sizeof(MessageLoop) == sizeof(MessageLoopForIO),
                MessageLoopForIO_should_not_have_extra_member_variables);
 
+}  // namespace base
+
+// TODO(brettw) remove this when all users are updated to explicitly use the
+// namespace
+using base::MessageLoop;
+using base::MessageLoopForIO;
+using base::MessageLoopForUI;
+
 #endif  // BASE_MESSAGE_LOOP_H_