message: Avoid relying on the Graph owned FunctionLibraryDefinition when partitioning the graph
  The partitioned graph will not inherit the function library from the original graph anymore.
  This is part of a series of change intended to decouple the FunctionLibraryDefinition
  from the Graph entirely.
diff: @@ -56,12 +56,9 @@ Status PartitionFunctionGraph(
  for (auto& partition : partitions) {
  const string& device = partition.first;
  GraphDef& graph_def = partition.second;
  - // Each partition gets a copy of all the
  - // std::unique_ptr<Graph> subgraph(new Graph(graph->flib_def()));
  + // Each partition gets a new graph.
  std::unique_ptr<Graph> subgraph(
  - new Graph(graph->flib_def().ReachableDefinitions(graph_def)));
  - FunctionLibraryDefinition global_flib(OpRegistry::Global(), {});
  - TF_CHECK_OK(subgraph->AddFunctionLibrary(global_flib.ToProto()));
  + new Graph(graph->flib_def().default_registry()));
  GraphConstructorOptions opts;
  opts.allow_internal_ops = true;
  opts.expect_device_spec = true;
  