cc : Store surface layer ids on LayerTreeHost and push them at commit

cc/trees/layer_tree_host_impl_unittest.cc

Index: cc/trees/layer_tree_host_impl_unittest.cc
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index a9e5a559a68a02739e4a0aea73abb2d1255eccb2..ac8929c5b3166c3c68eb70cddb490107caf2b47e 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -3463,7 +3463,9 @@ TEST_F(LayerTreeHostImplTest, EmbeddedSurfacesInMetadata) {
   std::vector<SurfaceId> children = {MakeSurfaceId(FrameSinkId(1, 1), 1),
                                      MakeSurfaceId(FrameSinkId(2, 2), 2),
                                      MakeSurfaceId(FrameSinkId(3, 3), 3)};
+  base::flat_set<SurfaceId> children_set;
   for (size_t i = 0; i < children.size(); ++i) {
+    children_set.insert(children[i]);
     std::unique_ptr<SurfaceLayerImpl> child =
         SurfaceLayerImpl::Create(host_impl_->active_tree(), i + 6);
     child->SetPosition(gfx::PointF(25.f * i, 0.f));
@@ -3476,6 +3478,7 @@ TEST_F(LayerTreeHostImplTest, EmbeddedSurfacesInMetadata) {
   }
 
   host_impl_->active_tree()->BuildPropertyTreesForTesting();
+  host_impl_->active_tree()->SetSurfaceLayerIds(children_set);
   DrawFrame();
 
   FakeCompositorFrameSink* fake_compositor_frame_sink =