Add support for (de)serializing LayerSelection.

cc/input/layer_selection_bound.cc

Index: cc/input/layer_selection_bound.cc
diff --git a/cc/input/layer_selection_bound.cc b/cc/input/layer_selection_bound.cc
index 9fcee2b4f01dc611035936a47996dc9a6118a29a..4e985157fcb63764b709a27a58853e57b26158ec 100644
--- a/cc/input/layer_selection_bound.cc
+++ b/cc/input/layer_selection_bound.cc
@@ -79,4 +79,20 @@ bool operator!=(const LayerSelectionBound& lhs,
   return !(lhs == rhs);
 }
 
+void LayerSelectionToProtobuf(const LayerSelection& selection,
+                              proto::LayerSelection* proto) {
+  selection.start.ToProtobuf(proto->mutable_start());
+  selection.end.ToProtobuf(proto->mutable_end());
+  proto->set_is_editable(selection.is_editable);
+  proto->set_is_empty_text_form_control(selection.is_empty_text_form_control);
+}
+
+void LayerSelectionFromProtobuf(LayerSelection* selection,
+                                const proto::LayerSelection& proto) {
+  selection->start.FromProtobuf(proto.start());
+  selection->end.FromProtobuf(proto.end());
+  selection->is_editable = proto.is_editable();
+  selection->is_empty_text_form_control = proto.is_empty_text_form_control();
+}
+
 }  // namespace cc