Implement non-zero dimension attribute parsing

Fixes #8445

The only attributes I found that we have implemented that uses non-zero
dimenion attributes:

* `width` for `<td>` and `<th>` (table cells)
* `width` for `<table>`

I updated these implementations to use the new non-zero dimension
attribute parsing and added associated regression tests.

1 files changed, 12 insertions, 0 deletions

diff --git a/components/util/str.rs b/components/util/str.rs
index 9978464ee0d..f00dd8e3ea7 100644
--- a/components/util/str.rs
+++ b/components/util/str.rs
@@ -4,6 +4,7 @@
 
 use app_units::Au;
 use cssparser::{self, Color, RGBA};
+use euclid::num::Zero;
 use js::conversions::{FromJSValConvertible, ToJSValConvertible, latin1_to_string};
 use js::jsapi::{JSContext, JSString, HandleValue, MutableHandleValue};
 use js::jsapi::{JS_GetTwoByteStringCharsAndLength, JS_StringHasLatin1Chars};
@@ -372,6 +373,17 @@ pub fn parse_length(mut value: &str) -> LengthOrPercentageOrAuto {
     }
 }
 
+/// HTML5 § 2.4.4.5.
+///
+/// https://html.spec.whatwg.org/multipage/#rules-for-parsing-non-zero-dimension-values
+pub fn parse_nonzero_length(value: &str) -> LengthOrPercentageOrAuto {
+    match parse_length(value) {
+        LengthOrPercentageOrAuto::Length(x) if x == Au::zero() => LengthOrPercentageOrAuto::Auto,
+        LengthOrPercentageOrAuto::Percentage(0.) => LengthOrPercentageOrAuto::Auto,
+        x => x,
+    }
+}
+
 /// https://html.spec.whatwg.org/multipage/#rules-for-parsing-a-legacy-font-size
 pub fn parse_legacy_font_size(mut input: &str) -> Option<&'static str> {
     // Steps 1 & 2 are not relevant