Remove calls to MessageLoop::current() in extensions.

extensions/browser/file_reader.h

Index: extensions/browser/file_reader.h
diff --git a/extensions/browser/file_reader.h b/extensions/browser/file_reader.h
index 109a97a8b47f2f07454f6a15d2207297b8dbd905..10a65ff6b8cff198e1903a69b1546caae16375e6 100644
--- a/extensions/browser/file_reader.h
+++ b/extensions/browser/file_reader.h
@@ -9,12 +9,9 @@
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
+#include "base/single_thread_task_runner.h"
 #include "extensions/common/extension_resource.h"
 
-namespace base {
-class MessageLoop;
-}
-
 // This file defines an interface for reading a file asynchronously on a
 // background thread.
 // Consider abstracting out a FilePathProvider (ExtensionResource) and moving
@@ -40,7 +37,7 @@ class FileReader : public base::RefCountedThreadSafe<FileReader> {
 
   extensions::ExtensionResource resource_;
   Callback callback_;
-  base::MessageLoop* origin_loop_;
+  const scoped_refptr<base::SingleThreadTaskRunner> origin_task_runner_;
 };
 
 #endif  // EXTENSIONS_BROWSER_FILE_READER_H_