diff --git a/components/style/properties/helpers.mako.rs b/components/style/properties/helpers.mako.rs
index 7156e9f9585..1c0c441ac63 100644
--- a/components/style/properties/helpers.mako.rs
+++ b/components/style/properties/helpers.mako.rs
@@ -333,9 +333,9 @@
 <%def name="single_keyword(name, values, vector=False, **kwargs)">
     <%call expr="single_keyword_computed(name, values, vector, **kwargs)">
         use values::computed::ComputedValueAsSpecified;
-        use values::NoViewportPercentage;
+        use values::HasViewportPercentage;
         impl ComputedValueAsSpecified for SpecifiedValue {}
-        impl NoViewportPercentage for SpecifiedValue {}
+        no_viewport_percentage!(SpecifiedValue);
     </%call>
 </%def>
 
diff --git a/components/style/properties/longhand/background.mako.rs b/components/style/properties/longhand/background.mako.rs
index ca790ab884c..e5cffa016c2 100644
--- a/components/style/properties/longhand/background.mako.rs
+++ b/components/style/properties/longhand/background.mako.rs
@@ -16,8 +16,8 @@ ${helpers.predefined_type("background-color", "CSSColor",
                           has_uncacheable_values="${product == 'gecko'}">
     use std::fmt;
     use style_traits::ToCss;
+    use values::HasViewportPercentage;
     use values::specified::Image;
-    use values::NoViewportPercentage;
 
     pub mod computed_value {
         use values::computed;
@@ -35,7 +35,7 @@ ${helpers.predefined_type("background-color", "CSSColor",
         }
     }
 
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     #[derive(Debug, Clone, PartialEq)]
     #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
diff --git a/components/style/properties/longhand/border.mako.rs b/components/style/properties/longhand/border.mako.rs
index b5c4ff6b1d3..55688015ed8 100644
--- a/components/style/properties/longhand/border.mako.rs
+++ b/components/style/properties/longhand/border.mako.rs
@@ -87,10 +87,10 @@ ${helpers.single_keyword("-moz-float-edge", "content-box margin-box",
                    spec="https://drafts.csswg.org/css-backgrounds/#border-image-source">
     use std::fmt;
     use style_traits::ToCss;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::specified::Image;
 
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     pub mod computed_value {
         use values::computed;
@@ -279,9 +279,9 @@ ${helpers.single_keyword("-moz-float-edge", "content-box margin-box",
                    spec="https://drafts.csswg.org/css-backgrounds/#border-image-repeat">
     use std::fmt;
     use style_traits::ToCss;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
 
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     pub mod computed_value {
         pub use super::RepeatKeyword;
@@ -557,10 +557,10 @@ ${helpers.single_keyword("-moz-float-edge", "content-box margin-box",
                    spec="https://drafts.csswg.org/css-backgrounds/#border-image-slice">
     use std::fmt;
     use style_traits::ToCss;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::specified::{Number, Percentage};
 
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     pub mod computed_value {
         use values::computed::Number;
diff --git a/components/style/properties/longhand/box.mako.rs b/components/style/properties/longhand/box.mako.rs
index 0e4abaaa1dc..aa30a5551ad 100644
--- a/components/style/properties/longhand/box.mako.rs
+++ b/components/style/properties/longhand/box.mako.rs
@@ -31,8 +31,8 @@
     %>
     use values::computed::ComputedValueAsSpecified;
     use style_traits::ToCss;
-    use values::NoViewportPercentage;
-    impl NoViewportPercentage for SpecifiedValue {}
+    use values::HasViewportPercentage;
+    no_viewport_percentage!(SpecifiedValue);
 
     pub mod computed_value {
         pub use super::SpecifiedValue as T;
@@ -113,8 +113,8 @@ ${helpers.single_keyword("-moz-top-layer", "none top",
         }
     }
 
-    use values::NoViewportPercentage;
-    impl NoViewportPercentage for SpecifiedValue {}
+    use values::HasViewportPercentage;
+    no_viewport_percentage!(SpecifiedValue);
     impl ToComputedValue for SpecifiedValue {
         type ComputedValue = computed_value::T;
 
@@ -152,8 +152,8 @@ ${helpers.single_keyword("-moz-top-layer", "none top",
                                   gecko_inexhaustive="True"
                                   gecko_ffi_name="mFloat"
                                   spec="https://drafts.csswg.org/css-box/#propdef-float">
-    use values::NoViewportPercentage;
-    impl NoViewportPercentage for SpecifiedValue {}
+    use values::HasViewportPercentage;
+    no_viewport_percentage!(SpecifiedValue);
     impl ToComputedValue for SpecifiedValue {
         type ComputedValue = computed_value::T;
 
@@ -194,8 +194,8 @@ ${helpers.single_keyword("-moz-top-layer", "none top",
                                   gecko_enum_prefix="StyleClear"
                                   gecko_ffi_name="mBreakType"
                                   spec="https://www.w3.org/TR/CSS2/visuren.html#flow-control">
-    use values::NoViewportPercentage;
-    impl NoViewportPercentage for SpecifiedValue {}
+    use values::HasViewportPercentage;
+    no_viewport_percentage!(SpecifiedValue);
     impl ToComputedValue for SpecifiedValue {
         type ComputedValue = computed_value::T;
 
@@ -396,9 +396,9 @@ ${helpers.single_keyword("overflow-x", "visible hidden scroll auto",
     use std::fmt;
     use style_traits::ToCss;
     use values::computed::ComputedValueAsSpecified;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
 
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     impl ToCss for SpecifiedValue {
         fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
@@ -442,8 +442,8 @@ ${helpers.single_keyword("overflow-x", "visible hidden scroll auto",
     use values::specified::Time;
 
     pub use values::specified::Time as SpecifiedValue;
-    use values::NoViewportPercentage;
-    impl NoViewportPercentage for SpecifiedValue {}
+    use values::HasViewportPercentage;
+    no_viewport_percentage!(SpecifiedValue);
 
     pub mod computed_value {
         pub use values::computed::Time as T;
@@ -703,8 +703,8 @@ ${helpers.single_keyword("overflow-x", "visible hidden scroll auto",
         }
     }
 
-    use values::NoViewportPercentage;
-    impl NoViewportPercentage for SpecifiedValue {}
+    use values::HasViewportPercentage;
+    no_viewport_percentage!(SpecifiedValue);
 
     #[inline]
     pub fn get_initial_value() -> computed_value::T {
@@ -745,8 +745,8 @@ ${helpers.single_keyword("overflow-x", "visible hidden scroll auto",
         SpecifiedValue::parse(input)
     }
 
-    use values::NoViewportPercentage;
-    impl NoViewportPercentage for SpecifiedValue {}
+    use values::HasViewportPercentage;
+    no_viewport_percentage!(SpecifiedValue);
 
     impl ComputedValueAsSpecified for SpecifiedValue { }
 </%helpers:vector_longhand>
@@ -773,7 +773,7 @@ ${helpers.single_keyword("overflow-x", "visible hidden scroll auto",
     use std::ops::Deref;
     use style_traits::ToCss;
     use values::computed::ComputedValueAsSpecified;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
 
     pub mod computed_value {
         pub use super::SpecifiedValue as T;
@@ -805,7 +805,7 @@ ${helpers.single_keyword("overflow-x", "visible hidden scroll auto",
             })
         }
     }
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     pub fn parse(context: &ParserContext, input: &mut Parser) -> Result<SpecifiedValue,()> {
         SpecifiedValue::parse(context, input)
@@ -847,7 +847,7 @@ ${helpers.single_keyword("overflow-x", "visible hidden scroll auto",
     use std::fmt;
     use style_traits::ToCss;
     use values::computed::ComputedValueAsSpecified;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
 
     pub mod computed_value {
         pub use super::SpecifiedValue as T;
@@ -885,7 +885,7 @@ ${helpers.single_keyword("overflow-x", "visible hidden scroll auto",
         }
     }
 
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     #[inline]
     pub fn get_initial_value() -> computed_value::T {
diff --git a/components/style/properties/longhand/column.mako.rs b/components/style/properties/longhand/column.mako.rs
index e10a69e45d1..f55524f5201 100644
--- a/components/style/properties/longhand/column.mako.rs
+++ b/components/style/properties/longhand/column.mako.rs
@@ -22,9 +22,9 @@ ${helpers.predefined_type("column-width",
                    spec="https://drafts.csswg.org/css-multicol/#propdef-column-count">
     use std::fmt;
     use style_traits::ToCss;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
 
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     #[derive(Debug, Clone, Copy, PartialEq)]
     #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
diff --git a/components/style/properties/longhand/counters.mako.rs b/components/style/properties/longhand/counters.mako.rs
index 78c9fa8fc9e..265e4b9bfe0 100644
--- a/components/style/properties/longhand/counters.mako.rs
+++ b/components/style/properties/longhand/counters.mako.rs
@@ -10,7 +10,7 @@
     use cssparser::Token;
     use std::ascii::AsciiExt;
     use values::computed::ComputedValueAsSpecified;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
 
     use super::list_style_type;
 
@@ -18,7 +18,7 @@
     pub use self::computed_value::ContentItem;
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     pub mod computed_value {
         use super::super::list_style_type;
@@ -179,7 +179,7 @@
     use std::fmt;
     use style_traits::ToCss;
     use super::content;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::computed::ComputedValueAsSpecified;
 
     use cssparser::{Token, serialize_identifier};
@@ -199,7 +199,7 @@
     }
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     impl ToCss for SpecifiedValue {
         fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
diff --git a/components/style/properties/longhand/font.mako.rs b/components/style/properties/longhand/font.mako.rs
index 42387415c1b..a52a7e1f498 100644
--- a/components/style/properties/longhand/font.mako.rs
+++ b/components/style/properties/longhand/font.mako.rs
@@ -11,12 +11,12 @@
 <%helpers:longhand name="font-family" animatable="False" need_index="True"
                    spec="https://drafts.csswg.org/css-fonts/#propdef-font-family">
     use self::computed_value::{FontFamily, FamilyName};
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::computed::ComputedValueAsSpecified;
     pub use self::computed_value::T as SpecifiedValue;
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     pub mod computed_value {
         use cssparser::CssStringWriter;
@@ -223,9 +223,9 @@ ${helpers.single_keyword("font-variant-caps",
                    spec="https://drafts.csswg.org/css-fonts/#propdef-font-weight">
     use std::fmt;
     use style_traits::ToCss;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
 
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     #[derive(Debug, Clone, PartialEq, Eq, Copy)]
     #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
@@ -458,12 +458,12 @@ ${helpers.single_keyword("font-variant-caps",
 
 <%helpers:longhand products="gecko" name="font-size-adjust" animatable="True"
                    spec="https://drafts.csswg.org/css-fonts/#propdef-font-size-adjust">
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::computed::ComputedValueAsSpecified;
     use values::specified::Number;
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     #[derive(Copy, Clone, Debug, PartialEq)]
     #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
@@ -520,11 +520,11 @@ ${helpers.single_keyword("font-variant-caps",
                    spec="https://drafts.csswg.org/css-fonts/#propdef-font-synthesis">
     use std::fmt;
     use style_traits::ToCss;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::computed::ComputedValueAsSpecified;
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     pub mod computed_value {
         pub use super::SpecifiedValue as T;
@@ -610,12 +610,12 @@ ${helpers.single_keyword("font-variant-position",
                    spec="https://drafts.csswg.org/css-fonts/#propdef-font-feature-settings">
     use std::fmt;
     use style_traits::ToCss;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::computed::ComputedValueAsSpecified;
     pub use self::computed_value::T as SpecifiedValue;
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     pub mod computed_value {
         use cssparser::Parser;
@@ -719,12 +719,12 @@ ${helpers.single_keyword("font-variant-position",
 // https://www.w3.org/TR/css-fonts-3/#propdef-font-language-override
 <%helpers:longhand name="font-language-override" products="none" animatable="False" extra_prefixes="moz"
                    spec="https://drafts.csswg.org/css-fonts-3/#propdef-font-language-override">
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::computed::ComputedValueAsSpecified;
     pub use self::computed_value::T as SpecifiedValue;
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     pub mod computed_value {
         use std::fmt;
diff --git a/components/style/properties/longhand/inherited_box.mako.rs b/components/style/properties/longhand/inherited_box.mako.rs
index 6a87bad5d15..ef19dedaca8 100644
--- a/components/style/properties/longhand/inherited_box.mako.rs
+++ b/components/style/properties/longhand/inherited_box.mako.rs
@@ -35,8 +35,8 @@ ${helpers.single_keyword("direction", "ltr rtl", need_clone=True, animatable=Fal
     animatable="False"
     spec="https://drafts.csswg.org/css-writing-modes/#propdef-text-orientation"
 >
-    use values::NoViewportPercentage;
-    impl NoViewportPercentage for SpecifiedValue {}
+    use values::HasViewportPercentage;
+    no_viewport_percentage!(SpecifiedValue);
 
     impl ToComputedValue for SpecifiedValue {
         type ComputedValue = computed_value::T;
@@ -91,8 +91,8 @@ ${helpers.single_keyword("image-rendering",
     use style_traits::ToCss;
     use values::specified::Angle;
 
-    use values::NoViewportPercentage;
-    impl NoViewportPercentage for SpecifiedValue {}
+    use values::HasViewportPercentage;
+    no_viewport_percentage!(SpecifiedValue);
 
     use std::f32::consts::PI;
     use values::CSSFloat;
@@ -225,9 +225,9 @@ ${helpers.single_keyword("image-rendering",
     use std::fmt;
     use style_traits::ToCss;
     use values::computed::ComputedValueAsSpecified;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
 
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     #[derive(Copy, Clone, Debug, Eq, PartialEq)]
     #[cfg_attr(feature = "servo", derive(HeapSizeOf, Deserialize, Serialize))]
diff --git a/components/style/properties/longhand/inherited_text.mako.rs b/components/style/properties/longhand/inherited_text.mako.rs
index 03b5eb2e33b..900dec4846c 100644
--- a/components/style/properties/longhand/inherited_text.mako.rs
+++ b/components/style/properties/longhand/inherited_text.mako.rs
@@ -204,9 +204,9 @@ ${helpers.single_keyword("text-align-last",
 <%helpers:longhand name="text-align" animatable="False" spec="https://drafts.csswg.org/css-text/#propdef-text-align">
     pub use self::computed_value::T as SpecifiedValue;
     use values::computed::ComputedValueAsSpecified;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
     pub mod computed_value {
         use style_traits::ToCss;
         macro_rules! define_text_align {
@@ -434,11 +434,11 @@ ${helpers.single_keyword("text-align-last",
     use cssparser::RGBA;
     use std::fmt;
     use style_traits::ToCss;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::computed::ComputedValueAsSpecified;
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     #[derive(Clone, PartialEq, Copy, Debug)]
     #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
@@ -518,9 +518,9 @@ ${helpers.single_keyword("text-align-last",
                                   animatable="False"
                                   spec="https://drafts.csswg.org/css-text/#propdef-white-space">
     use values::computed::ComputedValueAsSpecified;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     impl SpecifiedValue {
         pub fn allow_wrap(&self) -> bool {
@@ -771,9 +771,9 @@ ${helpers.single_keyword("text-align-last",
     use std::fmt;
     use style_traits::ToCss;
     use unicode_segmentation::UnicodeSegmentation;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
 
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     pub mod computed_value {
         #[derive(Debug, Clone, PartialEq)]
@@ -977,7 +977,7 @@ ${helpers.single_keyword("text-align-last",
                    spec="https://drafts.csswg.org/css-text-decor/#propdef-text-emphasis-position">
     use std::fmt;
     use values::computed::ComputedValueAsSpecified;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use style_traits::ToCss;
 
     define_css_keyword_enum!(HorizontalWritingModeValue:
@@ -996,7 +996,7 @@ ${helpers.single_keyword("text-align-last",
     }
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     pub fn get_initial_value() -> computed_value::T {
         SpecifiedValue(HorizontalWritingModeValue::Over, VerticalWritingModeValue::Right)
diff --git a/components/style/properties/longhand/list.mako.rs b/components/style/properties/longhand/list.mako.rs
index 9f19d80aec7..b0cfc32f56c 100644
--- a/components/style/properties/longhand/list.mako.rs
+++ b/components/style/properties/longhand/list.mako.rs
@@ -39,7 +39,7 @@ ${helpers.predefined_type("list-style-image", "UrlOrNone", "Either::Second(None_
     use std::fmt;
     use style_traits::ToCss;
     use values::computed::ComputedValueAsSpecified;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
 
     pub use self::computed_value::T as SpecifiedValue;
 
@@ -50,7 +50,7 @@ ${helpers.predefined_type("list-style-image", "UrlOrNone", "Either::Second(None_
     }
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     impl ToCss for SpecifiedValue {
         fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
diff --git a/components/style/properties/longhand/outline.mako.rs b/components/style/properties/longhand/outline.mako.rs
index e4fb0512d85..9780ac24110 100644
--- a/components/style/properties/longhand/outline.mako.rs
+++ b/components/style/properties/longhand/outline.mako.rs
@@ -20,7 +20,6 @@ ${helpers.predefined_type("outline-color", "CSSColor", "::cssparser::Color::Curr
     use std::fmt;
     use style_traits::ToCss;
     use values::specified::BorderStyle;
-    use values::NoViewportPercentage;
     use values::computed::ComputedValueAsSpecified;
 
     pub type SpecifiedValue = Either<Auto, BorderStyle>;
diff --git a/components/style/properties/longhand/pointing.mako.rs b/components/style/properties/longhand/pointing.mako.rs
index 71c43b2cc2b..a6219a32d1f 100644
--- a/components/style/properties/longhand/pointing.mako.rs
+++ b/components/style/properties/longhand/pointing.mako.rs
@@ -8,12 +8,12 @@
 
 <%helpers:longhand name="cursor" animatable="False" spec="https://drafts.csswg.org/css-ui/#cursor">
     pub use self::computed_value::T as SpecifiedValue;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::computed::ComputedValueAsSpecified;
     use values::specified::url::SpecifiedUrl;
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     pub mod computed_value {
         use std::fmt;
diff --git a/components/style/properties/longhand/position.mako.rs b/components/style/properties/longhand/position.mako.rs
index adb66cdc3a4..73b11432aaa 100644
--- a/components/style/properties/longhand/position.mako.rs
+++ b/components/style/properties/longhand/position.mako.rs
@@ -24,11 +24,11 @@
 % endfor
 
 <%helpers:longhand name="z-index" spec="https://www.w3.org/TR/CSS2/visuren.html#z-index" animatable="True">
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::computed::ComputedValueAsSpecified;
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
     pub type SpecifiedValue = computed_value::T;
     pub mod computed_value {
         use std::fmt;
diff --git a/components/style/properties/longhand/svg.mako.rs b/components/style/properties/longhand/svg.mako.rs
index b75a9c26255..9e68d5386af 100644
--- a/components/style/properties/longhand/svg.mako.rs
+++ b/components/style/properties/longhand/svg.mako.rs
@@ -62,7 +62,7 @@ ${helpers.single_keyword("mask-type", "luminance alpha",
                    spec="https://drafts.fxtf.org/css-masking/#propdef-clip-path">
     use std::fmt;
     use style_traits::ToCss;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::specified::basic_shape::{ShapeSource, GeometryBox};
 
     pub mod computed_value {
@@ -83,7 +83,7 @@ ${helpers.single_keyword("mask-type", "luminance alpha",
         ShapeSource::parse(context, input)
     }
 
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 </%helpers:longhand>
 
 ${helpers.single_keyword("mask-mode",
@@ -196,7 +196,7 @@ ${helpers.single_keyword("mask-composite",
     use std::sync::Arc;
     use values::specified::Image;
     use values::specified::url::SpecifiedUrl;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
 
     pub mod computed_value {
         use std::fmt;
@@ -222,7 +222,7 @@ ${helpers.single_keyword("mask-composite",
         }
     }
 
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     #[derive(Debug, Clone, PartialEq)]
     #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
diff --git a/components/style/properties/longhand/text.mako.rs b/components/style/properties/longhand/text.mako.rs
index a4325c7a0cc..8d1792c046b 100644
--- a/components/style/properties/longhand/text.mako.rs
+++ b/components/style/properties/longhand/text.mako.rs
@@ -16,12 +16,12 @@
                    spec="https://drafts.csswg.org/css-ui/#propdef-text-overflow">
     use std::fmt;
     use style_traits::ToCss;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::computed::ComputedValueAsSpecified;
     use cssparser;
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     #[derive(PartialEq, Eq, Clone, Debug)]
     #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
@@ -108,11 +108,11 @@ ${helpers.single_keyword("unicode-bidi",
                    spec="https://drafts.csswg.org/css-text-decor/#propdef-text-decoration-line">
     use std::fmt;
     use style_traits::ToCss;
-    use values::NoViewportPercentage;
+    use values::HasViewportPercentage;
     use values::computed::ComputedValueAsSpecified;
 
     impl ComputedValueAsSpecified for SpecifiedValue {}
-    impl NoViewportPercentage for SpecifiedValue {}
+    no_viewport_percentage!(SpecifiedValue);
 
     #[derive(PartialEq, Eq, Copy, Clone, Debug)]
     #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
diff --git a/components/style/values/mod.rs b/components/style/values/mod.rs
index 7a7d7baafea..4665b37ad82 100644
--- a/components/style/values/mod.rs
+++ b/components/style/values/mod.rs
@@ -47,6 +47,19 @@ macro_rules! define_numbered_css_keyword_enum {
     }
 }
 
+/// A macro used to implement HasViewportPercentage trait
+/// for a given type that may never contain viewport units.
+macro_rules! no_viewport_percentage {
+    ($name: ident) => {
+        impl HasViewportPercentage for $name {
+            #[inline]
+            fn has_viewport_percentage(&self) -> bool {
+                false
+            }
+        }
+    };
+}
+
 pub mod computed;
 pub mod specified;
 
@@ -62,18 +75,7 @@ pub trait HasViewportPercentage {
     fn has_viewport_percentage(&self) -> bool;
 }
 
-/// A trait used as a marker to represent that a given type may never contain
-/// viewport units.
-pub trait NoViewportPercentage {}
 
-impl<T> HasViewportPercentage for T
-    where T: NoViewportPercentage,
-{
-    #[inline]
-    fn has_viewport_percentage(&self) -> bool {
-        false
-    }
-}
 
 use self::computed::ComputedValueAsSpecified;
 
@@ -103,7 +105,7 @@ macro_rules! define_keyword_type {
         }
 
         impl ComputedValueAsSpecified for $name {}
-        impl NoViewportPercentage for $name {}
+        no_viewport_percentage!($name);
     };
 }
 
diff --git a/components/style/values/specified/grid.rs b/components/style/values/specified/grid.rs
index 1e414799ed9..4f3e64142e7 100644
--- a/components/style/values/specified/grid.rs
+++ b/components/style/values/specified/grid.rs
@@ -8,7 +8,7 @@ use cssparser::Parser;
 use parser::{Parse, ParserContext};
 use std::fmt;
 use style_traits::ToCss;
-use values::NoViewportPercentage;
+use values::HasViewportPercentage;
 use values::computed::ComputedValueAsSpecified;
 
 #[derive(PartialEq, Clone, Debug)]
@@ -96,4 +96,4 @@ impl Parse for GridLine {
 }
 
 impl ComputedValueAsSpecified for GridLine {}
-impl NoViewportPercentage for GridLine {}
+no_viewport_percentage!(GridLine);
diff --git a/components/style/values/specified/mod.rs b/components/style/values/specified/mod.rs
index 076324cebe6..dac10f661f7 100644
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@@ -16,7 +16,7 @@ use std::f32::consts::PI;
 use std::fmt;
 use std::ops::Mul;
 use style_traits::ToCss;
-use super::{CSSFloat, HasViewportPercentage, NoViewportPercentage, Either, None_};
+use super::{CSSFloat, HasViewportPercentage, Either, None_};
 use super::computed::{ComputedValueAsSpecified, Context, ToComputedValue};
 use super::computed::Shadow as ComputedShadow;
 
@@ -35,7 +35,7 @@ pub mod length;
 pub mod position;
 pub mod url;
 
-impl NoViewportPercentage for i32 {}  // For PropertyDeclaration::Order
+no_viewport_percentage!(i32);  // For PropertyDeclaration::Order
 
 #[derive(Clone, PartialEq, Debug)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
@@ -60,7 +60,7 @@ impl Parse for CSSColor {
     }
 }
 
-impl NoViewportPercentage for CSSColor {}
+no_viewport_percentage!(CSSColor);
 
 impl ToCss for CSSColor {
     fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
@@ -79,7 +79,7 @@ pub struct CSSRGBA {
     pub authored: Option<String>,
 }
 
-impl NoViewportPercentage for CSSRGBA {}
+no_viewport_percentage!(CSSRGBA);
 
 impl ToCss for CSSRGBA {
     fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
@@ -193,7 +193,7 @@ pub fn parse_number(input: &mut Parser) -> Result<f32, ()> {
 #[allow(missing_docs)]
 pub struct BorderRadiusSize(pub Size2D<LengthOrPercentage>);
 
-impl NoViewportPercentage for BorderRadiusSize {}
+no_viewport_percentage!(BorderRadiusSize);
 
 impl BorderRadiusSize {
     #[allow(missing_docs)]
@@ -402,7 +402,7 @@ define_numbered_css_keyword_enum! { BorderStyle:
     "outset" => outset = 2,
 }
 
-impl NoViewportPercentage for BorderStyle {}
+no_viewport_percentage!(BorderStyle);
 
 impl BorderStyle {
     /// Whether this border style is either none or hidden.
@@ -462,7 +462,7 @@ impl ToCss for Time {
 #[allow(missing_docs)]
 pub struct Number(pub CSSFloat);
 
-impl NoViewportPercentage for Number {}
+no_viewport_percentage!(Number);
 
 impl Parse for Number {
     fn parse(_context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
@@ -512,7 +512,7 @@ impl ToCss for Number {
 #[allow(missing_docs)]
 pub struct Opacity(pub CSSFloat);
 
-impl NoViewportPercentage for Opacity {}
+no_viewport_percentage!(Opacity);
 
 impl Parse for Opacity {
     fn parse(_context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
diff --git a/components/style/values/specified/url.rs b/components/style/values/specified/url.rs
index de58714c74f..9ce58980050 100644
--- a/components/style/values/specified/url.rs
+++ b/components/style/values/specified/url.rs
@@ -15,7 +15,7 @@ use std::borrow::Cow;
 use std::fmt::{self, Write};
 use std::sync::Arc;
 use style_traits::ToCss;
-use values::NoViewportPercentage;
+use values::HasViewportPercentage;
 use values::computed::ComputedValueAsSpecified;
 
 /// A set of data needed in Gecko to represent a URL.
@@ -202,4 +202,4 @@ impl ToCss for SpecifiedUrl {
 // TODO(emilio): Maybe consider ComputedUrl to save a word in style structs?
 impl ComputedValueAsSpecified for SpecifiedUrl {}
 
-impl NoViewportPercentage for SpecifiedUrl {}
+no_viewport_percentage!(SpecifiedUrl);