Add support for (de)serializing cc::Layer hierarchy.

cc/BUILD.gn

Index: cc/BUILD.gn
diff --git a/cc/BUILD.gn b/cc/BUILD.gn
index 6bd6aa2e5064e5f7e56b7c0e9de5d8a9e58f8c24..c2b653b66fc8c7d2757f8e5e59e519341b5ee122 100644
--- a/cc/BUILD.gn
+++ b/cc/BUILD.gn
@@ -132,12 +132,18 @@ component("cc") {
     "layers/layer.cc",
     "layers/layer.h",
     "layers/layer_client.h",
+    "layers/layer_deserializer.cc",
+    "layers/layer_deserializer.h",
     "layers/layer_impl.cc",
     "layers/layer_impl.h",
     "layers/layer_iterator.h",
     "layers/layer_lists.h",
     "layers/layer_position_constraint.cc",
     "layers/layer_position_constraint.h",
+    "layers/layer_proto_factory.cc",
+    "layers/layer_proto_factory.h",
+    "layers/layer_serializer.cc",
+    "layers/layer_serializer.h",
     "layers/layer_utils.cc",
     "layers/layer_utils.h",
     "layers/nine_patch_layer.cc",
@@ -738,6 +744,7 @@ test("cc_unittests") {
     "layers/heads_up_display_layer_impl_unittest.cc",
     "layers/heads_up_display_unittest.cc",
     "layers/io_surface_layer_impl_unittest.cc",
+    "layers/layer_deserializer_unittest.cc",
     "layers/layer_impl_unittest.cc",
     "layers/layer_iterator_unittest.cc",
     "layers/layer_position_constraint_unittest.cc",