message: Add test case for NONE ("") compression type with decode_compressed
diff: @@ -34,7 +34,9 @@ from tensorflow.python.platform import test
  class DecodeCompressedOpTest(test.TestCase):
  def _compress(self, bytes, compression_type):
  - if compression_type == "ZLIB":
  + if compression_type == "":
  + return bytes
  + elif compression_type == "ZLIB":
  return zlib.compress(bytes)
  else:
  out = StringIO()
  @@ -43,7 +45,7 @@ class DecodeCompressedOpTest(test.TestCase):
  return out.getvalue()
  def testDecompress(self):
  - for compression_type in ["ZLIB", "GZIP"]:
  + for compression_type in ["ZLIB", "GZIP", ""]:
  with self.test_session():
  in_bytes = array_ops.placeholder(dtypes.string, shape=[2])
  decompressed = parsing_ops.decode_compressed(
  @@ -56,7 +58,7 @@ class DecodeCompressedOpTest(test.TestCase):
  self.assertAllEqual(["AaAA", "bBbb"], result)
  def testDecompressWithRaw(self):
  - for compression_type in ["ZLIB", "GZIP"]:
  + for compression_type in ["ZLIB", "GZIP", ""]:
  with self.test_session():
  in_bytes = array_ops.placeholder(dtypes.string, shape=[None])
  decompressed = parsing_ops.decode_compressed(
  