Converts mash to use Shell

ash/shell_init_params.h

Index: ash/shell_init_params.h
diff --git a/ash/shell_init_params.h b/ash/shell_init_params.h
index 58495908a60b9283a8bf4921f600ee200ff6ae2b..d2f01e6b07661690b63aba9210b4b5f458c6f13d 100644
--- a/ash/shell_init_params.h
+++ b/ash/shell_init_params.h
@@ -7,6 +7,10 @@
 
 #include "ash/ash_export.h"
 
+namespace aura {
+class WindowTreeHostMus;
+}
+
 namespace base {
 class SequencedWorkerPool;
 }
@@ -20,6 +24,12 @@ namespace ash {
 class ShellDelegate;
 
 struct ASH_EXPORT ShellInitParams {
+  // Shell takes ownership of |wm_shell|, if null WmShellAura is created.
+  // TODO(sky): temporary, will eventually go away.
+  WmShell* wm_shell = nullptr;
+  // Shell takes ownership of |primary_window_tree_host|. This is only used
+  // by mash.
+  aura::WindowTreeHostMus* primary_window_tree_host = nullptr;
   ShellDelegate* delegate = nullptr;
   ui::ContextFactory* context_factory = nullptr;
   ui::ContextFactoryPrivate* context_factory_private = nullptr;