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

services/ui/common/gpu_service.cc

Index: services/ui/common/gpu_service.cc
diff --git a/services/ui/common/gpu_service.cc b/services/ui/common/gpu_service.cc
index 9a2f4c561a3e4b28576250d2b1782b026dcdc69e..f8bf9e79e0939d11ced35b5e1313616fe85c0011 100644
--- a/services/ui/common/gpu_service.cc
+++ b/services/ui/common/gpu_service.cc
@@ -47,18 +47,21 @@
 
 GpuService::~GpuService() {
   DCHECK(IsMainThread());
-  DCHECK_EQ(this, g_gpu_service);
   if (gpu_channel_)
     gpu_channel_->DestroyChannel();
-  g_gpu_service = nullptr;
 }
 
 // static
-std::unique_ptr<GpuService> GpuService::Initialize(
-    shell::Connector* connector) {
+void GpuService::Initialize(shell::Connector* connector) {
   DCHECK(!g_gpu_service);
   g_gpu_service = new GpuService(connector);
-  return base::WrapUnique(g_gpu_service);
+}
+
+// static
+void GpuService::Terminate() {
+  DCHECK(g_gpu_service);
+  delete g_gpu_service;
+  g_gpu_service = nullptr;
 }
 
 // static