Bug 1218257 - Use a different property other than word-spacing for a test. r=me

word-spacing is still using the old Gecko computed style storage, which means
that it has a little bit of precision loss that I just fixed for stroke-width.

testing/web-platform/meta/svg/painting/parsing/stroke-width-computed.svg.ini

@@ -1,7 +0,0 @@
-[stroke-width-computed.svg]
-  [stroke-width computes mm lengths]
-    expected: FAIL
-    bug: Precision difference with non-Servo serialization.
-  [stroke-width computes Q lengths]
-    expected: FAIL
-    bug: Precision difference with non-Servo serialization.

testing/web-platform/tests/svg/painting/parsing/stroke-width-computed.svg

@@ -50,9 +50,9 @@ for (let lengthUnit of lengthUnits) {
     target.style.strokeWidth = length;
 
     const ref = document.getElementById('ref');
-    ref.style.wordSpacing = length;
+    ref.style.textIndent = length;
 
-    assert_equals(getComputedStyle(target).strokeWidth, getComputedStyle(ref).wordSpacing);
+    assert_equals(getComputedStyle(target).strokeWidth, getComputedStyle(ref).textIndent);
   }, 'stroke-width computes ' + lengthUnit + ' lengths');
 }