Merged commit includes the following changes:

200617269  by A. Unique TensorFlower:

    Internal change

--
200603378  by jpienaar:

    The output of the merge should be the value's and not the original output port.

    The output port of the IfOp is already taken into account by selecting the
    merge node and the output of the merge should be the value used (which is the 0th
    output of the merge node).

--
200601721  by A. Unique TensorFlower:

    Basic support for tf.tile that multiplies a single axis.

--
200600686  by A. Unique TensorFlower:

    Internal change.

--

PiperOrigin-RevId: 200617269