Make cc::SurfaceId unguessable

cc/surfaces/display_unittest.cc

Index: cc/surfaces/display_unittest.cc
diff --git a/cc/surfaces/display_unittest.cc b/cc/surfaces/display_unittest.cc
index 312c3a4a9da65012ed9833c6baa246ab547be933..d629a52e4b630a186f85569a9427acdc8e023ae4 100644
--- a/cc/surfaces/display_unittest.cc
+++ b/cc/surfaces/display_unittest.cc
@@ -195,7 +195,8 @@ TEST_F(DisplayTest, DisplayDamaged) {
   display.Initialize(std::move(output_surface_), task_runner_.get());
   TestDisplayScheduler& scheduler = display.scheduler();
 
-  SurfaceId surface_id(id_allocator_.GenerateId());
+  SurfaceId surface_id;
+  surface_id = id_allocator_.GenerateId();
   EXPECT_FALSE(scheduler.damaged);
   EXPECT_FALSE(scheduler.has_new_root_surface);
   display.SetSurfaceId(surface_id, 1.f);
@@ -451,14 +452,15 @@ TEST_F(DisplayTest, Finish) {
 
   EXPECT_CALL(*context_ptr, shallowFinishCHROMIUM()).Times(0);
 
-  SurfaceId surface_id(id_allocator_.GenerateId());
+  SurfaceId surface_id;
+  surface_id = id_allocator_.GenerateId();
 
   TestDisplayClient client;
   RendererSettings settings;
   settings.partial_swap_enabled = true;
   settings.finish_rendering_on_resize = true;
   TestDisplay display(&client, &manager_, shared_bitmap_manager_.get(), nullptr,
-                      settings, surface_id.id_namespace());
+                      settings, surface_id.id_namespace);
   display.Initialize(std::move(output_surface_), task_runner_.get());
 
   display.SetSurfaceId(surface_id, 1.f);