gpu: Have GpuService create and own GpuMemoryBufferFactory.

services/ui/ws/gpu_host_unittest.cc

Index: services/ui/ws/gpu_host_unittest.cc
diff --git a/services/ui/ws/gpu_host_unittest.cc b/services/ui/ws/gpu_host_unittest.cc
index 9b4b338ece69e07310ef2c2c3278e372a094313d..e1cded771738d34418e614d082d474f334dee4a3 100644
--- a/services/ui/ws/gpu_host_unittest.cc
+++ b/services/ui/ws/gpu_host_unittest.cc
@@ -53,8 +53,7 @@ class TestGpuService : public GpuService {
 
 TestGpuService::TestGpuService()
     : GpuService(gpu::GPUInfo(),
-                 nullptr,
-                 nullptr,
+                 nullptr /* watchdog_thread */,
                  base::ThreadTaskRunnerHandle::Get(),
                  gpu::GpuFeatureInfo()) {}