Replace LayerImpl::sorting_context_id with transform reference.

cc/layers/surface_layer_impl_unittest.cc

Index: cc/layers/surface_layer_impl_unittest.cc
diff --git a/cc/layers/surface_layer_impl_unittest.cc b/cc/layers/surface_layer_impl_unittest.cc
index 6f7eab16fba06394551763d631915d8e766a714c..051de521cacb633733430185960f5b89fb9f6413 100644
--- a/cc/layers/surface_layer_impl_unittest.cc
+++ b/cc/layers/surface_layer_impl_unittest.cc
@@ -76,6 +76,7 @@ TEST(SurfaceLayerImplTest, SurfaceStretchedToLayerBounds) {
   // aspect ratios.
   gfx::Size layer_size(400, 100);
   gfx::Size surface_size(300, 300);
+  gfx::Size viewport_size(1000, 1000);
   float surface_scale = 1.f;
   gfx::Transform target_space_transform(
       surface_layer_impl->draw_properties().target_space_transform);
@@ -89,6 +90,8 @@ TEST(SurfaceLayerImplTest, SurfaceStretchedToLayerBounds) {
       SurfaceInfo(surface_id, surface_scale, surface_size));
   surface_layer_impl->SetStretchContentToFillBounds(true);
 
+  impl.CalcDrawProps(viewport_size);
+
   std::unique_ptr<RenderPass> render_pass = RenderPass::Create();
   AppendQuadsData data;
   surface_layer_impl->AppendQuads(render_pass.get(), &data);