Move MessageLoop to base namespace.

content/public/browser/url_data_source.h

Index: content/public/browser/url_data_source.h
diff --git a/content/public/browser/url_data_source.h b/content/public/browser/url_data_source.h
index 49daf872e9f5dda466c3831664e0af04be8a2cf9..93d38c0c2ae71c1675c7951a39ad456acb0a950b 100644
--- a/content/public/browser/url_data_source.h
+++ b/content/public/browser/url_data_source.h
@@ -10,9 +10,8 @@
 #include "base/callback.h"
 #include "content/common/content_export.h"
 
-class MessageLoop;
-
 namespace base {
+class MessageLoop;
 class RefCountedMemory;
 }
 
@@ -66,7 +65,8 @@ class CONTENT_EXPORT URLDataSource {
   // on the IO thread.  This can improve performance by satisfying such requests
   // more rapidly when there is a large amount of UI thread contention. Or the
   // delegate can return a specific thread's Messageloop if they wish.
-  virtual MessageLoop* MessageLoopForRequestPath(const std::string& path) const;
+  virtual base::MessageLoop* MessageLoopForRequestPath(
+      const std::string& path) const;
 
   // Returns true if the URLDataSource should replace an existing URLDataSource
   // with the same name that has already been registered. The default is true.