accept 'auto' only for CSS properties that allow it

Instead of handling the 'auto' value implicitly for all CSS
properties that accept lenght types, we now accept it only for
specific properties where 'auto' is valid according to CSS 2.1.
This fixes an assertion with the following HTML fragment:

<div style="background:auto">hello</div>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/css.hh b/src/css.hh
index 29f0b24a..a7143c27 100644
--- a/src/css.hh
+++ b/src/css.hh
@@ -37,6 +37,8 @@ typedef enum {
                                    'margin-*-width'). */
    CSS_TYPE_SIGNED_LENGTH,      /* As CSS_TYPE_LENGTH but may be negative. */
    CSS_TYPE_LENGTH_PERCENTAGE_NUMBER,  /* <length> or <percentage>, or <number> */
+   CSS_TYPE_AUTO,               /* Represented as CssLength of type
+                                   CSS_LENGTH_TYPE_AUTO */
    CSS_TYPE_COLOR,              /* Represented as integer. */
    CSS_TYPE_FONT_WEIGHT,        /* this very special and only used by
                                    'font-weight' */