message: Re-added proto field for dynamic learning rate support (not usable yet).
diff: @@ -9,8 +9,8 @@ message ClippingLimits {
  google.protobuf.FloatValue upper = 2; // +inf if not set
  }
  -// Get the learning rate from a <yet to be determined> source that can change
  -// dynamically.
  +// Get the learning rate from the parameters of the SendTPUEmbeddingGradients
  +// op.
  message DynamicLearningRate {
  }
  @@ -18,10 +18,8 @@ message DynamicLearningRate {
  message LearningRate {
  oneof learning_rate {
  float constant = 1;
  - // DynamicLearningRate dynamic = 2; -- disabled while code is being
  - // rewritten.
  + DynamicLearningRate dynamic = 2;
  }
  - reserved 2;
  }
  message AdagradParameters {
  