message: Add float16 support for tf.contrib.image.transform
  This fix tries to address the issue raised in 20243 where
  there were no float16 support for tf.contrib.image.transform.
  This fix adds the float16 support and enables related tests.
  This fix fixes 20243.
diff: @@ -33,7 +33,7 @@ _image_ops_so = loader.load_op_library(
  resource_loader.get_path_to_datafile("_image_ops.so"))
  _IMAGE_DTYPES = set(
  - [dtypes.uint8, dtypes.int32, dtypes.int64, dtypes.float32, dtypes.float64])
  + [dtypes.uint8, dtypes.int32, dtypes.int64, dtypes.float16, dtypes.float32, dtypes.float64])
  ops.RegisterShape("ImageConnectedComponents")(common_shapes.call_cpp_shape_fn)
  ops.RegisterShape("ImageProjectiveTransform")(common_shapes.call_cpp_shape_fn)
  