Remove the inherited_style getter from StyleBuilder.

The concept of inherited style is about to get a bit more complicated, and this
will prevent consumers from doing it wrong.

Part 1 of Gecko bug1382806.  r=emilio

components/style/properties/helpers/animated_properties.mako.rs

@@ -605,8 +605,8 @@ impl AnimationValue {
                                 CSSWideKeyword::Unset |
                             % endif
                             CSSWideKeyword::Inherit => {
-                                let inherit_struct = context.inherited_style()
+                                let inherit_struct = context.builder
-                                                            .get_${prop.style_struct.name_lower}();
+                                                            .get_parent_${prop.style_struct.name_lower}();
                                 inherit_struct.clone_${prop.ident}()
                             },
                         };

components/style/properties/longhand/color.mako.rs

@@ -22,7 +22,7 @@
         #[inline]
         fn to_computed_value(&self, context: &Context) -> computed_value::T {
             self.0.to_computed_value(context)
-                .to_rgba(context.inherited_style().get_color().clone_color())
+                .to_rgba(context.builder.get_parent_color().clone_color())
         }
 
         #[inline]

components/style/properties/longhand/font.mako.rs

@@ -548,9 +548,9 @@ ${helpers.single_keyword_system("font-variant-caps",
                 SpecifiedValue::Normal => computed_value::T::normal(),
                 SpecifiedValue::Bold => computed_value::T::bold(),
                 SpecifiedValue::Bolder =>
-                    context.inherited_style().get_font().clone_font_weight().bolder(),
+                    context.builder.get_parent_font().clone_font_weight().bolder(),
                 SpecifiedValue::Lighter =>
-                    context.inherited_style().get_font().clone_font_weight().lighter(),
+                    context.builder.get_parent_font().clone_font_weight().lighter(),
                 SpecifiedValue::System(_) => {
                     <%self:nongecko_unreachable>
                         context.cached_system_font.as_ref().unwrap().font_weight.clone()
@@ -940,7 +940,7 @@ ${helpers.single_keyword_system("font-variant-caps",
             // recomputed from the base size for the keyword and the relative size.
             //
             // See bug 1355707
-            if let Some((kw, fraction)) = context.builder.inherited_style().font_computation_data.font_size_keyword {
+            if let Some((kw, fraction)) = context.builder.inherited_font_computation_data().font_size_keyword {
                 context.builder.font_size_keyword = Some((kw, fraction * ratio));
             } else {
                 context.builder.font_size_keyword = None;
@@ -956,9 +956,9 @@ ${helpers.single_keyword_system("font-variant-caps",
             // if the language or generic changed, we need to recalculate
             // the font size from the stored font-size origin information.
             if context.builder.get_font().gecko().mLanguage.raw::<nsIAtom>() !=
-               context.builder.inherited_style().get_font().gecko().mLanguage.raw::<nsIAtom>() ||
+               context.builder.get_parent_font().gecko().mLanguage.raw::<nsIAtom>() ||
                context.builder.get_font().gecko().mGenericID !=
-               context.builder.inherited_style().get_font().gecko().mGenericID {
+               context.builder.get_parent_font().gecko().mGenericID {
                 if let Some((kw, ratio)) = context.builder.font_size_keyword {
                     computed = kw.to_computed_value(context).scale_by(ratio);
                 }
@@ -968,8 +968,7 @@ ${helpers.single_keyword_system("font-variant-caps",
         let device = context.builder.device;
         let mut font = context.builder.take_font();
         let parent_unconstrained = {
-            let parent_style = context.builder.inherited_style();
+            let parent_font = context.builder.get_parent_font();
-            let parent_font = parent_style.get_font();
             font.apply_font_size(computed, parent_font, device)
         };
         context.builder.put_font(font);
@@ -997,9 +996,8 @@ ${helpers.single_keyword_system("font-variant-caps",
         let device = context.builder.device;
         let mut font = context.builder.take_font();
         let used_kw = {
-            let parent_style = context.builder.inherited_style();
+            let parent_font = context.builder.get_parent_font();
-            let parent_font = parent_style.get_font();
+            parent_kw = context.builder.inherited_font_computation_data().font_size_keyword;
-            parent_kw = parent_style.font_computation_data.font_size_keyword;
 
             font.inherit_font_size_from(parent_font, kw_inherited_size, device)
         };
@@ -2279,8 +2277,8 @@ https://drafts.csswg.org/css-fonts-4/#low-level-font-variation-settings-control-
 
             let int = match *self {
                 SpecifiedValue::Auto => {
-                    let parent = cx.inherited_style().get_font().clone__moz_script_level() as i32;
+                    let parent = cx.builder.get_parent_font().clone__moz_script_level() as i32;
-                    let display = cx.inherited_style().get_font().clone__moz_math_display();
+                    let display = cx.builder.get_parent_font().clone__moz_math_display();
                     if display == DisplayValue::inline {
                         parent + 1
                     } else {
@@ -2288,7 +2286,7 @@ https://drafts.csswg.org/css-fonts-4/#low-level-font-variation-settings-control-
                     }
                 }
                 SpecifiedValue::Relative(rel) => {
-                    let parent = cx.inherited_style().get_font().clone__moz_script_level();
+                    let parent = cx.builder.get_parent_font().clone__moz_script_level();
                     parent as i32 + rel
                 }
                 SpecifiedValue::Absolute(abs) => abs,

components/style/properties/longhand/inherited_text.mako.rs

@@ -230,8 +230,8 @@ ${helpers.single_keyword("text-align-last",
                         if context.is_root_element {
                             return get_initial_value();
                         }
-                        let parent = context.inherited_style().get_inheritedtext().clone_text_align();
+                        let parent = context.builder.get_parent_inheritedtext().clone_text_align();
-                        let ltr = context.inherited_style().writing_mode.is_bidi_ltr();
+                        let ltr = context.builder.inherited_writing_mode().is_bidi_ltr();
                         match (parent, ltr) {
                             (computed_value::T::start, true) => computed_value::T::left,
                             (computed_value::T::start, false) => computed_value::T::right,
@@ -241,7 +241,7 @@ ${helpers.single_keyword("text-align-last",
                         }
                     }
                     SpecifiedValue::MozCenterOrInherit => {
-                        let parent = context.inherited_style().get_inheritedtext().clone_text_align();
+                        let parent = context.builder.get_parent_inheritedtext().clone_text_align();
                         if parent == computed_value::T::start {
                             computed_value::T::center
                         } else {
@@ -340,7 +340,7 @@ ${helpers.predefined_type("word-spacing",
                 overline: None,
                 line_through: None,
             },
-            _ => context.inherited_style().get_inheritedtext().clone__servo_text_decorations_in_effect()
+            _ => context.builder.get_parent_inheritedtext().clone__servo_text_decorations_in_effect()
         };
 
         result.underline = maybe(context.style().get_text().has_underline()

components/style/properties/properties.mako.rs

@@ -2655,11 +2655,6 @@ impl<'a> StyleBuilder<'a> {
         self.visited_style.is_some()
     }
 
-    /// Returns the style we're inheriting from.
-    pub fn inherited_style(&self) -> &'a ComputedValues {
-        self.inherited_style
-    }
-
     /// Returns the style we're getting reset properties from.
     pub fn default_style(&self) -> &'a ComputedValues {
         self.reset_style
@@ -2752,6 +2747,38 @@ impl<'a> StyleBuilder<'a> {
     fn custom_properties(&self) -> Option<Arc<::custom_properties::CustomPropertiesMap>> {
         self.custom_properties.clone()
     }
+
+    /// Access to various information about our inherited styles.  We don't
+    /// expose an inherited ComputedValues directly, because in the
+    /// ::first-line case some of the inherited information needs to come from
+    /// one ComputedValues instance and some from a different one.
+
+    /// Inherited font bits.
+    pub fn inherited_font_computation_data(&self) -> &FontComputationData {
+        &self.inherited_style.font_computation_data
+    }
+
+    /// Inherited writing-mode.
+    pub fn inherited_writing_mode(&self) -> &WritingMode {
+        &self.inherited_style.writing_mode
+    }
+
+    /// Inherited style flags.
+    pub fn inherited_flags(&self) -> &ComputedValueFlags {
+        &self.inherited_style.flags
+    }
+
+    /// And access to inherited style structs.
+    % for style_struct in data.active_style_structs():
+        /// Gets our inherited `${style_struct.name}`.  We don't name these
+        /// accessors `inherited_${style_struct.name_lower}` because we already
+        /// have things like "box" vs "inherited_box" as struct names.  Do the
+        /// next-best thing and call them `parent_${style_struct.name_lower}`
+        /// instead.
+        pub fn get_parent_${style_struct.name_lower}(&self) -> &style_structs::${style_struct.name} {
+            self.inherited_style.get_${style_struct.name_lower}()
+        }
+    % endfor
 }
 
 #[cfg(feature = "servo")]

components/style/style_adjuster.rs

@@ -446,7 +446,7 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
         let relevant_link_visited = if flags.contains(IS_LINK) {
             flags.contains(IS_VISITED_LINK)
         } else {
-            self.style.inherited_style().flags.contains(IS_RELEVANT_LINK_VISITED)
+            self.style.inherited_flags().contains(IS_RELEVANT_LINK_VISITED)
         };
 
         if relevant_link_visited {

components/style/values/computed/mod.rs

@@ -119,11 +119,6 @@ impl<'a> Context<'a> {
         self.builder.device.au_viewport_size()
     }
 
-    /// The style we're inheriting from.
-    pub fn inherited_style(&self) -> &ComputedValues {
-        self.builder.inherited_style()
-    }
-
     /// The default computed style we're getting our reset style from.
     pub fn default_style(&self) -> &ComputedValues {
         self.builder.default_style()
@@ -411,7 +406,7 @@ impl ToComputedValue for specified::JustifyItems {
         // If the inherited value of `justify-items` includes the `legacy` keyword, `auto` computes
         // to the inherited value.
         if self.0 == align::ALIGN_AUTO {
-            let inherited = context.inherited_style().get_position().clone_justify_items();
+            let inherited = context.builder.get_parent_position().clone_justify_items();
             if inherited.0.contains(align::ALIGN_LEGACY) {
                 return inherited
             }

components/style/values/specified/length.rs

@@ -93,7 +93,7 @@ impl FontBaseSize {
         match *self {
             FontBaseSize::Custom(size) => size,
             FontBaseSize::CurrentStyle => context.style().get_font().clone_font_size(),
-            FontBaseSize::InheritedStyle => context.inherited_style().get_font().clone_font_size(),
+            FontBaseSize::InheritedStyle => context.style().get_parent_font().clone_font_size(),
         }
     }
 }