Remove use of deprecated MessageLoop methods in extensions.

extensions/renderer/gc_callback.cc

Index: extensions/renderer/gc_callback.cc
diff --git a/extensions/renderer/gc_callback.cc b/extensions/renderer/gc_callback.cc
index 46b7f8acdf1e847eee51ad6dc229ece2cba95f47..012189791ea23ec00409665861ce95281178015a 100644
--- a/extensions/renderer/gc_callback.cc
+++ b/extensions/renderer/gc_callback.cc
@@ -5,7 +5,9 @@
 #include "extensions/renderer/gc_callback.h"
 
 #include "base/bind.h"
-#include "base/message_loop/message_loop.h"
+#include "base/location.h"
+#include "base/single_thread_task_runner.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "extensions/renderer/script_context.h"
 
 namespace extensions {
@@ -35,7 +37,7 @@ void GCCallback::OnObjectGC(const v8::WeakCallbackInfo<GCCallback>& data) {
   // code is RunCallback.
   GCCallback* self = data.GetParameter();
   self->object_.Reset();
-  base::MessageLoop::current()->PostTask(
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE, base::Bind(&GCCallback::RunCallback,
                             self->weak_ptr_factory_.GetWeakPtr()));
 }