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 a92496c75214ae5070f0d08a1891d2343f81432e..b909ee64fd1ba8073b4905a0fb36c1cd169fdc33 100644
--- a/cc/surfaces/display_unittest.cc
+++ b/cc/surfaces/display_unittest.cc
@@ -163,7 +163,7 @@ 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);
 
@@ -188,7 +188,7 @@ 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);
@@ -421,7 +421,7 @@ 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));