diff --git a/components/style/properties/longhand/position.mako.rs b/components/style/properties/longhand/position.mako.rs
index 3f995b10873..263e45579f3 100644
--- a/components/style/properties/longhand/position.mako.rs
+++ b/components/style/properties/longhand/position.mako.rs
@@ -13,7 +13,8 @@
     ${helpers.predefined_type(side, "LengthOrPercentageOrAuto",
                               "computed::LengthOrPercentageOrAuto::Auto",
                               spec="https://www.w3.org/TR/CSS2/visuren.html#propdef-%s" % side,
-                              animation_value_type="ComputedValue")}
+                              animation_value_type="ComputedValue",
+                              allow_quirks=True)}
 % endfor
 // offset-* logical properties, map to "top" / "left" / "bottom" / "right"
 % for side in LOGICAL_SIDES:
diff --git a/components/style/values/specified/length.rs b/components/style/values/specified/length.rs
index 424e6553279..830a6bb4554 100644
--- a/components/style/values/specified/length.rs
+++ b/components/style/values/specified/length.rs
@@ -1307,15 +1307,19 @@ impl ToCss for LengthOrPercentageOrAuto {
 }
 
 impl LengthOrPercentageOrAuto {
-    fn parse_internal(context: &ParserContext, input: &mut Parser, num_context: AllowedLengthType)
+    fn parse_internal(context: &ParserContext,
+                      input: &mut Parser,
+                      num_context: AllowedLengthType,
+                      allow_quirks: AllowQuirks)
                       -> Result<Self, ()> {
         match try!(input.next()) {
             Token::Dimension(ref value, ref unit) if num_context.is_ok(value.value) =>
                 NoCalcLength::parse_dimension(context, value.value, unit).map(LengthOrPercentageOrAuto::Length),
             Token::Percentage(ref value) if num_context.is_ok(value.unit_value) =>
                 Ok(LengthOrPercentageOrAuto::Percentage(Percentage(value.unit_value))),
-            Token::Number(ref value) if value.value == 0. => {
-                if value.value != 0. && !context.length_parsing_mode.allows_unitless_lengths() {
+            Token::Number(ref value) if num_context.is_ok(value.value) => {
+                if value.value != 0. && !context.length_parsing_mode.allows_unitless_lengths() &&
+                   !allow_quirks.allowed(context.quirks_mode) {
                     return Err(())
                 }
                 Ok(LengthOrPercentageOrAuto::Length(
@@ -1337,7 +1341,7 @@ impl LengthOrPercentageOrAuto {
     /// Parse a non-negative length, percentage, or auto.
     #[inline]
     pub fn parse_non_negative(context: &ParserContext, input: &mut Parser) -> Result<LengthOrPercentageOrAuto, ()> {
-        Self::parse_internal(context, input, AllowedLengthType::NonNegative)
+        Self::parse_internal(context, input, AllowedLengthType::NonNegative, AllowQuirks::No)
     }
 
     /// Returns the `auto` value.
@@ -1354,7 +1358,18 @@ impl LengthOrPercentageOrAuto {
 impl Parse for LengthOrPercentageOrAuto {
     #[inline]
     fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
-        Self::parse_internal(context, input, AllowedLengthType::All)
+        Self::parse_quirky(context, input, AllowQuirks::No)
+    }
+}
+
+impl LengthOrPercentageOrAuto {
+    /// Parses, with quirks.
+    #[inline]
+    pub fn parse_quirky(context: &ParserContext,
+                        input: &mut Parser,
+                        allow_quirks: AllowQuirks)
+                        -> Result<Self, ()> {
+        Self::parse_internal(context, input, AllowedLengthType::All, allow_quirks)
     }
 }
 
diff --git a/tests/wpt/metadata/quirks-mode/unitless-length.html.ini b/tests/wpt/metadata/quirks-mode/unitless-length.html.ini
index aec7eace770..870dcb0d8e8 100644
--- a/tests/wpt/metadata/quirks-mode/unitless-length.html.ini
+++ b/tests/wpt/metadata/quirks-mode/unitless-length.html.ini
@@ -1,13 +1,16 @@
 [unitless-length.html]
   type: testharness
   [bottom: 1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [clip: 1 (quirks)]
     expected: FAIL
@@ -60,20 +63,20 @@
   [padding: 1 (quirks)]
     expected: FAIL
 
-  [right: 1 (quirks)]
-    expected: FAIL
-
   [text-indent: 1 (quirks)]
     expected: FAIL
 
   [top: 1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [vertical-align: 1 (quirks)]
     expected: FAIL
@@ -85,13 +88,16 @@
     expected: FAIL
 
   [bottom: +1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [clip: +1 (quirks)]
     expected: FAIL
@@ -144,20 +150,20 @@
   [padding: +1 (quirks)]
     expected: FAIL
 
-  [right: +1 (quirks)]
-    expected: FAIL
-
   [text-indent: +1 (quirks)]
     expected: FAIL
 
   [top: +1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [vertical-align: +1 (quirks)]
     expected: FAIL
@@ -169,13 +175,16 @@
     expected: FAIL
 
   [bottom: -1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [clip: -1 (quirks)]
     expected: FAIL
@@ -198,20 +207,20 @@
   [padding: -1 (quirks)]
     expected: FAIL
 
-  [right: -1 (quirks)]
-    expected: FAIL
-
   [text-indent: -1 (quirks)]
     expected: FAIL
 
   [top: -1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [vertical-align: -1 (quirks)]
     expected: FAIL
@@ -220,13 +229,16 @@
     expected: FAIL
 
   [bottom: 1.5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1.5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1.5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [clip: 1.5 (quirks)]
     expected: FAIL
@@ -279,20 +291,20 @@
   [padding: 1.5 (quirks)]
     expected: FAIL
 
-  [right: 1.5 (quirks)]
-    expected: FAIL
-
   [text-indent: 1.5 (quirks)]
     expected: FAIL
 
   [top: 1.5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1.5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1.5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [vertical-align: 1.5 (quirks)]
     expected: FAIL
@@ -304,13 +316,16 @@
     expected: FAIL
 
   [bottom: +1.5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1.5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1.5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [clip: +1.5 (quirks)]
     expected: FAIL
@@ -363,20 +378,20 @@
   [padding: +1.5 (quirks)]
     expected: FAIL
 
-  [right: +1.5 (quirks)]
-    expected: FAIL
-
   [text-indent: +1.5 (quirks)]
     expected: FAIL
 
   [top: +1.5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1.5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1.5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [vertical-align: +1.5 (quirks)]
     expected: FAIL
@@ -388,13 +403,16 @@
     expected: FAIL
 
   [bottom: -1.5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1.5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1.5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [clip: -1.5 (quirks)]
     expected: FAIL
@@ -417,20 +435,20 @@
   [padding: -1.5 (quirks)]
     expected: FAIL
 
-  [right: -1.5 (quirks)]
-    expected: FAIL
-
   [text-indent: -1.5 (quirks)]
     expected: FAIL
 
   [top: -1.5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1.5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1.5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [vertical-align: -1.5 (quirks)]
     expected: FAIL
@@ -439,742 +457,988 @@
     expected: FAIL
 
   [bottom: \\31  (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: \\31  (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: \\31  (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: \\31  (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: \\31  (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: \\31  (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +\\31  (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +\\31  (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +\\31  (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +\\31  (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +\\31  (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +\\31  (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -\\31  (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -\\31  (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -\\31  (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -\\31  (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -\\31  (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -\\31  (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: \\31 .5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: \\31 .5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: \\31 .5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: \\31 .5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: \\31 .5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: \\31 .5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +\\31 .5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +\\31 .5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +\\31 .5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +\\31 .5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +\\31 .5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +\\31 .5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -\\31 .5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -\\31 .5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -\\31 .5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -\\31 .5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -\\31 .5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -\\31 .5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1\\31  (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1\\31  (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1\\31  (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1\\31  (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1\\31  (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1\\31  (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1\\31  (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1\\31  (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1\\31  (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1\\31  (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1\\31  (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1\\31  (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1\\31  (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1\\31  (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1\\31  (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1\\31  (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1\\31  (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1\\31  (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1\\31 .5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1\\31 .5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1\\31 .5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1\\31 .5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1\\31 .5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1\\31 .5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1\\31 .5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1\\31 .5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1\\31 .5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1\\31 .5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1\\31 .5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1\\31 .5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1\\31 .5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1\\31 .5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1\\31 .5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1\\31 .5 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1\\31 .5 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1\\31 .5 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: A (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: A (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: A (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: A (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: A (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: A (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: 1a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: 1a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1A (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1A (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +1A (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1A (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1A (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +1A (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1A (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1A (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -1A (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1A (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1A (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -1A (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +A (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +A (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +A (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +A (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +A (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +A (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -A (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -A (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -A (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -A (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -A (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -A (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: @a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: @a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: @a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: @a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: @a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: @a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: @1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: @1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: @1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: @1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: @1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: @1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: @1a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: @1a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: @1a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: @1a (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: @1a (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: @1a (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: "a" (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: "a" (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: "a" (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: "a" (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: "a" (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: "a" (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: "1" (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: "1" (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: "1" (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: "1" (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: "1" (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: "1" (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: "1a" (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: "1a" (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: "1a" (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: "1a" (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: "1a" (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: "1a" (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: url(1) (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: url(1) (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: url(1) (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: url(1) (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: url(1) (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: url(1) (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: url('1') (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: url('1') (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: url('1') (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: url('1') (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: url('1') (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: url('1') (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #01 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #01 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #01 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #01 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #01 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #01 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #001 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #001 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #001 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #001 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #001 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #001 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #0001 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #0001 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #0001 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #0001 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #0001 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #0001 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #00001 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #00001 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #00001 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #00001 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #00001 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #00001 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #000001 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #000001 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: #000001 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #000001 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #000001 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: #000001 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +/**/1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +/**/1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: +/**/1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +/**/1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +/**/1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: +/**/1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -/**/1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -/**/1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: -/**/1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -/**/1 (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -/**/1 (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: -/**/1 (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: calc(1) (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: calc(1) (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: calc(1) (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: calc(1) (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: calc(1) (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: calc(1) (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: calc(2 * 2px) (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: calc(2 * 2px) (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [bottom: calc(2 * 2px) (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: calc(2 * 2px) (quirks)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: calc(2 * 2px) (almost standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [top: calc(2 * 2px) (standards)]
-    expected: FAIL
+    expected:
+      if os == "mac": FAIL
 
   [margin: 1px 2 (quirks)]
     expected: FAIL