message: Update documentation for GraphOptimizer::Optimize's return value.
diff: @@ -39,7 +39,7 @@ class GraphOptimizer {
  // Routine called to allow an algorithm to propose a rewritten graph
  // for the graph, feeds and fetches in "item" to run more efficiently
  // on "cluster".
  - // Returns true iff it managed to generate a solution, false otherwise.
  + // Returns an error status if it failed to generate a solution.
  virtual Status Optimize(Cluster* cluster, const GrapplerItem& item,
  GraphDef* optimized_graph) = 0;
  