Removes usage of Compositor/ContextFactory methods

mojo/aura/window_tree_host_mojo.cc

Index: mojo/aura/window_tree_host_mojo.cc
diff --git a/mojo/aura/window_tree_host_mojo.cc b/mojo/aura/window_tree_host_mojo.cc
index f3e42d1931c22294756c756520934f2e15bae0e3..e944fdbb22d8092179607a850b1df2d78d27d739 100644
--- a/mojo/aura/window_tree_host_mojo.cc
+++ b/mojo/aura/window_tree_host_mojo.cc
@@ -40,12 +40,10 @@ WindowTreeHostMojo::WindowTreeHostMojo(
 
   // The ContextFactory must exist before any Compositors are created.
   if (context_factory_) {
-    ui::ContextFactory::SetInstance(NULL);
     delete context_factory_;
     context_factory_ = NULL;
   }
   context_factory_ = new ContextFactoryMojo(pipe.handle1.Pass());
-  ui::ContextFactory::SetInstance(context_factory_);
   aura::Env::GetInstance()->set_context_factory(context_factory_);
   CHECK(context_factory_) << "No GL bindings.";
 }