Reusing base::IdType<...> to implement SurfaceId.

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 9c90ce08b342e77413c7e34fbf75a1ab75352050..3d3ecd7b39449df098863623ce660d445b488893 100644
--- a/cc/surfaces/display_unittest.cc
+++ b/cc/surfaces/display_unittest.cc
@@ -166,7 +166,7 @@ TEST_F(DisplayTest, DisplayAsSurfaceAggregatorClient) {
                                  task_runner_.get());
   display.Initialize(std::move(output_surface_), &scheduler);
 
-  SurfaceId surface_id(6);
+  SurfaceId surface_id = SurfaceId::FromUnsafeValue(6);
   factory_.Create(surface_id);
   Surface* surface = manager_.GetSurfaceForId(surface_id);
 
@@ -191,7 +191,7 @@ TEST_F(DisplayTest, DisplayDamaged) {
                                  task_runner_.get());
   display.Initialize(std::move(output_surface_), &scheduler);
 
-  SurfaceId surface_id(7u);
+  SurfaceId surface_id = SurfaceId::FromUnsafeValue(7u);
   EXPECT_FALSE(scheduler.damaged);
   EXPECT_FALSE(scheduler.has_new_root_surface);
   display.SetSurfaceId(surface_id, 1.f);
@@ -448,7 +448,7 @@ TEST_F(DisplayTest, Finish) {
                                  task_runner_.get());
   display.Initialize(std::move(output_surface_), &scheduler);
 
-  SurfaceId surface_id(7u);
+  SurfaceId surface_id = SurfaceId::FromUnsafeValue(7u);
   display.SetSurfaceId(surface_id, 1.f);
 
   display.Resize(gfx::Size(100, 100));