Flow inlines around floats (#30243)

This implements the rest of the bulk of float support. Now inline
element flow around floats and floats can be pushed down by inline
elements before them.

Co-authored-by: Oriol Brufau <obrufau@igalia.com>

components/layout_2020/geom.rs

@@ -105,11 +105,11 @@ where
     }
 }
 
-impl flow_relative::Vec2<Length> {
+impl<T: Zero> flow_relative::Vec2<T> {
     pub fn zero() -> Self {
         Self {
-            inline: Length::zero(),
-            block: Length::zero(),
+            inline: T::zero(),
+            block: T::zero(),
         }
     }
 }
@@ -155,7 +155,7 @@ impl flow_relative::Vec2<Option<&'_ LengthPercentage>> {
     }
 }
 
-impl flow_relative::Rect<Length> {
+impl<T: Zero> flow_relative::Rect<T> {
     pub fn zero() -> Self {
         Self {
             start_corner: flow_relative::Vec2::zero(),
@@ -346,6 +346,17 @@ where
     }
 }
 
+impl<T: Zero> flow_relative::Sides<T> {
+    pub(crate) fn zero() -> flow_relative::Sides<T> {
+        flow_relative::Sides {
+            inline_start: T::zero(),
+            inline_end: T::zero(),
+            block_start: T::zero(),
+            block_end: T::zero(),
+        }
+    }
+}
+
 impl<T> flow_relative::Rect<T> {
     pub fn max_inline_position(&self) -> T
     where

components/layout_2020/style_ext.rs

@@ -65,6 +65,17 @@ pub(crate) struct PaddingBorderMargin {
     pub padding_border_sums: flow_relative::Vec2<Length>,
 }
 
+impl PaddingBorderMargin {
+    pub(crate) fn zero() -> Self {
+        Self {
+            padding: flow_relative::Sides::zero(),
+            border: flow_relative::Sides::zero(),
+            margin: flow_relative::Sides::zero(),
+            padding_border_sums: flow_relative::Vec2::zero(),
+        }
+    }
+}
+
 pub(crate) trait ComputedValuesExt {
     fn inline_size_is_length(&self) -> bool;
     fn inline_box_offsets_are_both_non_auto(&self) -> bool;