[mojo] Replace MessageLoopProxy usage with ThreadTaskRunnerHandle

mojo/runner/child_process.cc

Index: mojo/runner/child_process.cc
diff --git a/mojo/runner/child_process.cc b/mojo/runner/child_process.cc
index cee831f57ec4bb96dd0496c7798114cee8acaa6f..64145e437ba41cdbd45ea6bc8b16970d7adefcc3 100644
--- a/mojo/runner/child_process.cc
+++ b/mojo/runner/child_process.cc
@@ -18,6 +18,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/thread_task_runner_handle.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_checker.h"
 #include "mojo/common/message_pump_mojo.h"
@@ -191,10 +192,11 @@ class ChildControllerImpl : public ChildController, public ErrorHandler {
         new ChildControllerImpl(app_context, unblocker));
 
     ScopedMessagePipeHandle host_message_pipe(embedder::CreateChannel(
-        platform_channel.Pass(), app_context->io_runner(),
+        platform_channel.Pass(),
+        app_context->io_runner(),
         base::Bind(&ChildControllerImpl::DidCreateChannel,
                    base::Unretained(impl.get())),
-        base::MessageLoopProxy::current()));
+        base::ThreadTaskRunnerHandle::Get()));
 
     impl->Bind(host_message_pipe.Pass());