Auto merge of #17705 - emilio:neg-padding, r=bholley

style: Avoid parsing negative padding in the padding shorthand.

Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=1380492

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components/style/properties/shorthand/padding.mako.rs

@@ -4,6 +4,6 @@
 
 <%namespace name="helpers" file="/helpers.mako.rs" />
 
-${helpers.four_sides_shorthand("padding", "padding-%s", "specified::LengthOrPercentage::parse",
+${helpers.four_sides_shorthand("padding", "padding-%s", "specified::LengthOrPercentage::parse_non_negative",
                                spec="https://drafts.csswg.org/css-box-3/#propdef-padding",
                                allow_quirks=True)}

tests/wpt/metadata-css/css21_dev/html4/c5510-padn-002.htm.ini

@@ -1,3 +0,0 @@
-[c5510-padn-002.htm]
-  type: reftest
-  expected: FAIL

tests/wpt/metadata-css/css21_dev/html4/padding-009.htm.ini

@@ -1,3 +0,0 @@
-[padding-009.htm]
-  type: reftest
-  expected: FAIL