message: Add metrics to track the usage of TensorflowOpLayers.
diff: @@ -36,6 +36,7 @@ from tensorflow.python.distribute import values as distribute_values
  from tensorflow.python.eager import context
  from tensorflow.python.eager import execute
  from tensorflow.python.eager import function
  +from tensorflow.python.eager import monitoring
  from tensorflow.python.framework import auto_control_deps
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  @@ -84,6 +85,9 @@ from tensorflow.tools.docs import doc_controls
  # Prefix that is added to the TF op layer names.
  _TF_OP_LAYER_NAME_PREFIX = 'tf_op_layer_'
  +_keras_layers_gauge = monitoring.BoolGauge('/tensorflow/api/keras/layers',
  + 'keras layers usage', 'method')
  +
  @keras_export('keras.layers.Layer')
  class Layer(module.Module):
  @@ -2549,6 +2553,7 @@ class TensorFlowOpLayer(Layer):
  super(TensorFlowOpLayer, self).__init__(
  name=_TF_OP_LAYER_NAME_PREFIX + name, trainable=trainable, dtype=dtype,
  autocast=False)
  + _keras_layers_gauge.get_cell('TensorflowOpLayer').set(True)
  if isinstance(node_def, dict):
  self.node_def = json_format.ParseDict(node_def, node_def_pb2.NodeDef())
  else:
  