content/child: Remove use of MessageLoopProxy and deprecated MessageLoop APIs

content/child/child_process.h

Index: content/child/child_process.h
diff --git a/content/child/child_process.h b/content/child/child_process.h
index cf3173f7132c4ee64b7b242bd059c4ac6b0798f4..32d5638b099865b80106cd019b2879a1ca7dc83c 100644
--- a/content/child/child_process.h
+++ b/content/child/child_process.h
@@ -43,8 +43,8 @@ class CONTENT_EXPORT ChildProcess {
   void set_main_thread(ChildThreadImpl* thread);
 
   base::MessageLoop* io_message_loop() { return io_thread_.message_loop(); }
-  base::MessageLoopProxy* io_message_loop_proxy() {
-    return io_thread_.message_loop_proxy().get();
+  base::SingleThreadTaskRunner* io_task_runner() {
+    return io_thread_.task_runner().get();
   }
 
   // A global event object that is signalled when the main thread's message