cc: Move LayerImpl::AddChild and RemoveChild to LayerImplTestProperties

cc/test/test_layer_tree_host_base.cc

Index: cc/test/test_layer_tree_host_base.cc
diff --git a/cc/test/test_layer_tree_host_base.cc b/cc/test/test_layer_tree_host_base.cc
index becc2c1dbdd6315302b5a9ea02fb6bf9a47dae83..214d72523d2d977f737c2730d52b233068d02e04 100644
--- a/cc/test/test_layer_tree_host_base.cc
+++ b/cc/test/test_layer_tree_host_base.cc
@@ -120,9 +120,8 @@ void TestLayerTreeHostBase::SetupPendingTree(
     pending_tree->SetRootLayer(std::move(new_pending_root));
   } else {
     pending_layer.reset(static_cast<FakePictureLayerImpl*>(
-        pending_root
-            ->RemoveChildForTesting(
-                pending_root->test_properties()->children[0])
+        pending_root->test_properties()
+            ->RemoveChild(pending_root->test_properties()->children[0])
             .release()));
     if (!tile_size.IsEmpty())
       pending_layer->set_fixed_tile_size(tile_size);
@@ -132,7 +131,7 @@ void TestLayerTreeHostBase::SetupPendingTree(
   pending_layer->SetBounds(raster_source->GetSize());
   pending_layer->SetRasterSourceOnPending(raster_source, invalidation);
 
-  pending_root->AddChild(std::move(pending_layer));
+  pending_root->test_properties()->AddChild(std::move(pending_layer));
   pending_tree->SetViewportLayersFromIds(Layer::INVALID_ID,
                                          pending_tree->root_layer()->id(),
                                          Layer::INVALID_ID, Layer::INVALID_ID);