Revert of [mojo] Replace MessageLoopProxy usage with ThreadTaskRunnerHandle

mojo/application/content_handler_factory.cc

Index: mojo/application/content_handler_factory.cc
diff --git a/mojo/application/content_handler_factory.cc b/mojo/application/content_handler_factory.cc
index a7e5d2cc53645caafbb6f9b9e2d6763e954303c6..8518f4c937ff4f3eb18dc1e15b6afdb6eb61ba5d 100644
--- a/mojo/application/content_handler_factory.cc
+++ b/mojo/application/content_handler_factory.cc
@@ -9,8 +9,6 @@
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/memory/weak_ptr.h"
-#include "base/single_thread_task_runner.h"
-#include "base/thread_task_runner_handle.h"
 #include "base/threading/platform_thread.h"
 #include "mojo/application/application_runner_chromium.h"
 #include "mojo/common/message_pump_mojo.h"
@@ -27,7 +25,7 @@
 class ApplicationThread : public base::PlatformThread::Delegate {
  public:
   ApplicationThread(
-      scoped_refptr<base::SingleThreadTaskRunner> handler_thread,
+      scoped_refptr<base::MessageLoopProxy> handler_thread,
       const base::Callback<void(ApplicationThread*)>& termination_callback,
       ContentHandlerFactory::Delegate* handler_delegate,
       InterfaceRequest<Application> application_request,
@@ -46,7 +44,7 @@
                               base::Bind(termination_callback_, this));
   }
 
-  scoped_refptr<base::SingleThreadTaskRunner> handler_thread_;
+  scoped_refptr<base::MessageLoopProxy> handler_thread_;
   base::Callback<void(ApplicationThread*)> termination_callback_;
   ContentHandlerFactory::Delegate* handler_delegate_;
   InterfaceRequest<Application> application_request_;
@@ -78,13 +76,11 @@
   // Overridden from ContentHandler:
   void StartApplication(InterfaceRequest<Application> application_request,
                         URLResponsePtr response) override {
-    ApplicationThread* thread =
-        new ApplicationThread(base::ThreadTaskRunnerHandle::Get(),
-                              base::Bind(&ContentHandlerImpl::OnThreadEnd,
-                                         weak_factory_.GetWeakPtr()),
-                              delegate_,
-                              application_request.Pass(),
-                              response.Pass());
+    ApplicationThread* thread = new ApplicationThread(
+        base::MessageLoopProxy::current(),
+        base::Bind(&ContentHandlerImpl::OnThreadEnd,
+                   weak_factory_.GetWeakPtr()),
+        delegate_, application_request.Pass(), response.Pass());
     base::PlatformThreadHandle handle;
     bool launched = base::PlatformThread::Create(0, thread, &handle);
     DCHECK(launched);