Adds DesktopWindowTreeHostMus

ui/aura/test/aura_mus_test_base.cc

Index: ui/aura/test/aura_mus_test_base.cc
diff --git a/ui/aura/test/aura_mus_test_base.cc b/ui/aura/test/aura_mus_test_base.cc
index f16074942ec77a4395c9e796ecd5e203a94a7aee..e89b1eb458428c6b4da8e02f7305ed08309058c9 100644
--- a/ui/aura/test/aura_mus_test_base.cc
+++ b/ui/aura/test/aura_mus_test_base.cc
@@ -12,7 +12,7 @@ AuraMusWmTestBase::AuraMusWmTestBase() {}
 AuraMusWmTestBase::~AuraMusWmTestBase() {}
 
 void AuraMusWmTestBase::SetUp() {
-  EnableMus();
+  EnableMusWithTestWindowTree();
   AuraTestBase::SetUp();
 }
 
@@ -21,7 +21,7 @@ AuraMusClientTestBase::AuraMusClientTestBase() {}
 AuraMusClientTestBase::~AuraMusClientTestBase() {}
 
 void AuraMusClientTestBase::SetUp() {
-  EnableMus();
+  EnableMusWithTestWindowTree();
   set_window_manager_delegate(nullptr);
   AuraTestBase::SetUp();
 }