mus: Rename GpuService to Gpu.

ash/mus/window_manager_application.h

Index: ash/mus/window_manager_application.h
diff --git a/ash/mus/window_manager_application.h b/ash/mus/window_manager_application.h
index 4c5abe8e7da669e849cd4799c09ea24f031bcbfe..54a2bfb7ffb4c4e4d95553e37970fc3ec36d001f 100644
--- a/ash/mus/window_manager_application.h
+++ b/ash/mus/window_manager_application.h
@@ -39,7 +39,7 @@ class AuraInit;
 }
 
 namespace ui {
-class GpuService;
+class Gpu;
 }
 
 namespace ash {
@@ -84,7 +84,7 @@ class WindowManagerApplication
 
   std::unique_ptr<views::AuraInit> aura_init_;
 
-  std::unique_ptr<ui::GpuService> gpu_service_;
+  std::unique_ptr<ui::Gpu> gpu_;
   std::unique_ptr<aura::MusContextFactory> compositor_context_factory_;
   std::unique_ptr<WindowManager> window_manager_;