message: Drop external control dependencies in tfe.defun.
  They shouldn't help given the automatic control dependencies, and are tricky
  to capture in the general case.
diff: @@ -269,6 +269,15 @@ class FuncGraph(ops.Graph):
  def variables(self, var_list):
  self._weak_variables = [weakref.ref(v) for v in var_list]
  + def control_dependencies(self, control_inputs):
  + # Drop control dependencies to outside of the graph. TODO(b/117109273)
  + # unclear how to capture an op, not a tensor.
  + if not control_inputs:
  + return super(FuncGraph, self).control_dependencies(control_inputs)
  + return super(FuncGraph, self).control_dependencies(
  + [c for c in control_inputs
  + if getattr(c, "graph", None) is self])
  +
  def create_op(
  self,
  op_type,
  