Resolve relative URLs in inline CSS relative to document's base URL, rather than its content URL.

This means passing the base URL as the URL param to LibCSS's
css_stylesheet_create, rather than the URL of the source of
the style data.

css/select.c

@@ -163,7 +163,7 @@ static css_select_handler selection_handler = {
  * \param data          Source data
  * \param len           Length of data in bytes
  * \param charset       Charset of data, or NULL if unknown
- * \param url           URL of document containing data
+ * \param url           Base URL of document containing data
  * \param allow_quirks  True to permit CSS parsing quirks
  * \return Pointer to stylesheet, or NULL on failure.
  */

render/box_construct.c

@@ -1338,7 +1338,7 @@ css_select_results *box_get_style(html_content *c,
 				(const uint8_t *) dom_string_data(s),
 				dom_string_byte_length(s),
 				c->encoding,
-				nsurl_access(content_get_url(&c->base)), 
+				nsurl_access(c->base_url),
 				c->quirks != DOM_DOCUMENT_QUIRKS_MODE_NONE);
 
 		dom_string_unref(s);