Remove separate thread for the shell on Android.

mojo/services/native_viewport/native_viewport_android.cc

Index: mojo/services/native_viewport/native_viewport_android.cc
diff --git a/mojo/services/native_viewport/native_viewport_android.cc b/mojo/services/native_viewport/native_viewport_android.cc
index 5c03a0afcb3da8116e6961d6dfe22c7715c5c4ab..bc8071662d81c0eee8f9a3e5a0267f5e833b3d1a 100644
--- a/mojo/services/native_viewport/native_viewport_android.cc
+++ b/mojo/services/native_viewport/native_viewport_android.cc
@@ -71,10 +71,7 @@ void NativeViewportAndroid::Init() {
   init->ui_runner = context_->task_runners()->ui_runner();
   init->native_viewport = GetWeakPtr();
 
-  context_->task_runners()->java_runner()->PostTask(FROM_HERE,
-      base::Bind(MojoViewport::CreateForActivity,
-                 context_->activity(),
-                 init));
+  MojoViewport::CreateForActivity(context_->activity(), init);
 }
 
 void NativeViewportAndroid::Close() {