mus: Rename GpuService to Gpu.

mash/simple_wm/simple_wm.cc

Index: mash/simple_wm/simple_wm.cc
diff --git a/mash/simple_wm/simple_wm.cc b/mash/simple_wm/simple_wm.cc
index 8ff0659f1ba8f3a7b1eb74fc02899cac5aec822c..03ef9527b6331fabcbb9a1057efe8669346e1de9 100644
--- a/mash/simple_wm/simple_wm.cc
+++ b/mash/simple_wm/simple_wm.cc
@@ -72,7 +72,7 @@ SimpleWM::~SimpleWM() {
   // WindowTreeClient destruction may callback to us.
   window_tree_client_.reset();
 
-  gpu_service_.reset();
+  gpu_.reset();
 
   display::Screen::SetScreenInstance(nullptr);
 }
@@ -85,9 +85,9 @@ void SimpleWM::OnStart() {
   aura_init_ = base::MakeUnique<views::AuraInit>(
       context()->connector(), context()->identity(), "views_mus_resources.pak",
       std::string(), nullptr, views::AuraInit::Mode::AURA_MUS_WINDOW_MANAGER);
-  gpu_service_ = ui::GpuService::Create(context()->connector(), nullptr);
+  gpu_ = ui::Gpu::Create(context()->connector(), nullptr);
   compositor_context_factory_ =
-      base::MakeUnique<aura::MusContextFactory>(gpu_service_.get());
+      base::MakeUnique<aura::MusContextFactory>(gpu_.get());
   aura::Env::GetInstance()->set_context_factory(
       compositor_context_factory_.get());
   window_tree_client_ = base::MakeUnique<aura::WindowTreeClient>(