Revert of services/ui: Have an explicit lifetime/ownership of ui::GpuService.

ash/mus/window_manager_application.cc

Index: ash/mus/window_manager_application.cc
diff --git a/ash/mus/window_manager_application.cc b/ash/mus/window_manager_application.cc
index d7131ec4b5e0299d682f5f0220afe49936803f46..247c760e19e09bed0e2b63c1097eeca068a2eead 100644
--- a/ash/mus/window_manager_application.cc
+++ b/ash/mus/window_manager_application.cc
@@ -78,7 +78,7 @@
   // Destroy the WindowManager while still valid. This way we ensure
   // OnWillDestroyRootWindowController() is called (if it hasn't been already).
   window_manager_.reset();
-  gpu_service_.reset();
+
   ShutdownComponents();
 }
 
@@ -96,7 +96,7 @@
 }
 
 void WindowManagerApplication::OnStart(const shell::Identity& identity) {
-  gpu_service_ = ui::GpuService::Initialize(connector());
+  ui::GpuService::Initialize(connector());
   window_manager_.reset(new WindowManager(connector()));
 
   aura_init_.reset(new views::AuraInit(connector(), "ash_mus_resources.pak"));