Revert of ash/mash: Add a mus-client that sets up ash to provide the system ui for mash.

ash/host/ash_window_tree_host.cc

Index: ash/host/ash_window_tree_host.cc
diff --git a/ash/host/ash_window_tree_host.cc b/ash/host/ash_window_tree_host.cc
index 0bc59558f36effcf81d2c04348067faf9a6147e0..5cbe067e6ec2fd13b38c13a3f361afaabfbebeeb 100644
--- a/ash/host/ash_window_tree_host.cc
+++ b/ash/host/ash_window_tree_host.cc
@@ -20,12 +20,6 @@
 #endif
 
 namespace ash {
-
-namespace {
-
-AshWindowTreeHost::Factory creation_factory;
-
-}  // namespace
 
 AshWindowTreeHost::AshWindowTreeHost() : input_method_handler_(nullptr) {
 }
@@ -55,12 +49,8 @@
   }
 }
 
-// static
 AshWindowTreeHost* AshWindowTreeHost::Create(
     const AshWindowTreeHostInitParams& init_params) {
-  if (!creation_factory.is_null())
-    return creation_factory.Run(init_params);
-
   if (init_params.offscreen)
     return new AshWindowTreeHostUnified(init_params.initial_bounds);
 #if defined(USE_OZONE)
@@ -74,9 +64,4 @@
 #endif
 }
 
-// static
-void AshWindowTreeHost::SetFactory(const Factory& factory) {
-  creation_factory = factory;
-}
-
 }  // namespace ash