Merged commit includes the following changes:

209663919  by yifeif<yifeif@google.com>:

    Internal change.

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209663914  by amitpatankar<amitpatankar@google.com>:

    Fix the topk_op_test for numpy>1.15.

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209660476  by jdduke<jdduke@google.com>:

    Fix model lifetime for TensorFlow Lite C# bindings

    Ensure the model's existence for the duration of the interpreter,
    as per API requirements.

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209655960  by scottzhu<scottzhu@google.com>:

    Unify RNN Cell interface between TF and Keras.

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209655731  by A. Unique TensorFlower<gardener@tensorflow.org>:

    Added tests for PredictionOps and PartitionExamplesOps

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209655291  by nolivia<nolivia@google.com>:

    adding rate class so that we can save global_step/sec using tf.contrib.summary.  The function takes the rate in relation to any tensors provided that the numerator and denominator are broadcastable and have dtypes that can be cast to float64

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209654655  by kramerb<kramerb@google.com>:

    [XLA] Switch from tensorflow::gtl::InlinedVector to absl::InlinedVector

    This one comes with extra goodies like a move constructor.

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209653851  by A. Unique TensorFlower<gardener@tensorflow.org>:

    Internal build specification change

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PiperOrigin-RevId: 209663919