Makes Env contain a ContextFactory

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index d2322d8d42e89c7d6cc339c7b0ffa0649ac9474d..c0a176517c1f7c883e2d26096454cb7f43f70fb0 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -843,10 +843,8 @@ void Shell::Init(const ShellInitParams& init_params) {
   // Shelf, and WallPaper could be created by the factory.
   views::FocusManagerFactory::Install(new AshFocusManagerFactory);
 
-  // Env creates the compositor. Historically it seems to have been implicitly
-  // initialized first by the ActivationController, but now that FocusController
-  // no longer does this we need to do it explicitly.
   aura::Env::CreateInstance(true);
+  aura::Env::GetInstance()->set_context_factory(init_params.context_factory);
 
   // The WindowModalityController needs to be at the front of the input event
   // pretarget handler list to ensure that it processes input events when modal