ui::ContextFactory should not create SurfaceIdAllocators

ash/sysui/stub_context_factory.cc

Index: ash/sysui/stub_context_factory.cc
diff --git a/ash/sysui/stub_context_factory.cc b/ash/sysui/stub_context_factory.cc
index ce7af105a52e917fadc38c0145c89db77e337821..44f7512c932555195dc1bf3aeff06490c73b4a8f 100644
--- a/ash/sysui/stub_context_factory.cc
+++ b/ash/sysui/stub_context_factory.cc
@@ -71,10 +71,8 @@ cc::TaskGraphRunner* StubContextFactory::GetTaskGraphRunner() {
   return task_graph_runner_.get();
 }
 
-std::unique_ptr<cc::SurfaceIdAllocator>
-StubContextFactory::CreateSurfaceIdAllocator() {
-  return base::WrapUnique(
-      new cc::SurfaceIdAllocator(next_surface_id_namespace_++));
+uint32_t StubContextFactory::AllocateSurfaceClientId() {
+  return next_surface_id_namespace_++;
 }
 
 cc::SurfaceManager* StubContextFactory::GetSurfaceManager() {