Remove calls to deprecated MessageLoop methods in gin.

gin/shell/gin_main.cc

Index: gin/shell/gin_main.cc
diff --git a/gin/shell/gin_main.cc b/gin/shell/gin_main.cc
index 5ac0a79850b6e63b753044001db2c58f70548f9e..e73ce1f6dd0a02cbae2675eae0ffe0b555fc9a75 100644
--- a/gin/shell/gin_main.cc
+++ b/gin/shell/gin_main.cc
@@ -12,6 +12,7 @@
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "gin/array_buffer.h"
@@ -101,6 +102,6 @@ int main(int argc, char** argv) {
         base::Bind(gin::Run, runner.GetWeakPtr(), base::FilePath(*it)));
   }
 
-  message_loop.RunUntilIdle();
+  base::RunLoop().RunUntilIdle();
   return 0;
 }