message: Change incorrect padding comment.
  The padded area is not zero-filled for pooling ops, despite the comment.
diff: @@ -38,7 +38,8 @@ class NodeDef;
  // dimensions as the input.
  // EXPLICIT: The user specifies the pad values in the explicit_paddings
  // attribute.
  -// The padded area is zero-filled.
  +// The padded area is typically zero-filled. For pooling ops, the padded area is
  +// instead ignored. For max pool, this is equivalent to padding with -infinity.
  enum Padding {
  VALID = 1, // No padding.
  SAME = 2, // Input and output layers have the same size.
  