refactor: use is_zero() instead of comparing with Au::Zero() (#36347)

Use `is_zero()` instead of comparing with `Au::Zero()` for zero checks. 

Testing: This change does not cause behaviour change, a test is not
necessary.
Fixes: #36300

---------

Signed-off-by: Barigbue <barigbuenbira@gmail.com>

components/layout_2020/Cargo.toml

@@ -58,4 +58,5 @@ webrender_api = { workspace = true }
 xi-unicode = { workspace = true }
 
 [dev-dependencies]
+num-traits = { workspace = true }
 quickcheck = "1"

components/layout_2020/flexbox/layout.rs

@@ -1071,7 +1071,7 @@ fn allocate_free_cross_space_for_flex_line(
     remaining_free_cross_space: Au,
     remaining_line_count: i32,
 ) -> (Au, Au) {
-    if remaining_free_cross_space == Au::zero() {
+    if remaining_free_cross_space.is_zero() {
         return (Au::zero(), Au::zero());
     }
 
@@ -1394,7 +1394,7 @@ impl InitialFlexLineLayout<'_> {
             //
             // FIXME: is it a problem if floating point precision errors accumulate
             // and we get not-quite-zero remaining free space when we should get zero here?
-            if remaining_free_space != Au::zero() {
+            if !remaining_free_space.is_zero() {
                 // > If using the flex grow factor:
                 // > For every unfrozen item on the line, find the ratio of the item’s flex grow factor to
                 // > the sum of the flex grow factors of all unfrozen items on the line. Set the item’s

components/layout_2020/flow/inline/mod.rs

@@ -1720,7 +1720,7 @@ impl InlineFormattingContext {
         let mut collapsible_margins_in_children = CollapsedBlockMargins::zero();
         let content_block_size = layout.current_line.start_position.block;
         collapsible_margins_in_children.collapsed_through = !layout.had_inflow_content &&
-            content_block_size == Au::zero() &&
+            content_block_size.is_zero() &&
             collapsible_with_parent_start_margin.0;
 
         CacheableLayoutResult {

components/layout_2020/flow/mod.rs

@@ -162,7 +162,7 @@ impl BlockLevelBox {
             _ => return false,
         };
 
-        if pbm.padding.block_start != Au::zero() || pbm.border.block_start != Au::zero() {
+        if !pbm.padding.block_start.is_zero() || !pbm.border.block_start.is_zero() {
             return false;
         }
 
@@ -215,7 +215,7 @@ impl BlockLevelBox {
 
         if !block_size_is_zero_or_intrinsic(style.content_block_size(), containing_block) ||
             !block_size_is_zero_or_intrinsic(style.min_block_size(), containing_block) ||
-            pbm.padding_border_sums.block != Au::zero()
+            !pbm.padding_border_sums.block.is_zero()
         {
             return false;
         }
@@ -907,7 +907,7 @@ fn layout_in_flow_non_replaced_block_level_same_formatting_context(
 
     let computed_block_size = style.content_block_size();
     let start_margin_can_collapse_with_children =
-        pbm.padding.block_start == Au::zero() && pbm.border.block_start == Au::zero();
+        pbm.padding.block_start.is_zero() && pbm.border.block_start.is_zero();
 
     let mut clearance = None;
     let parent_containing_block_position_info;
@@ -1024,14 +1024,14 @@ fn layout_in_flow_non_replaced_block_level_same_formatting_context(
     }
 
     let collapsed_through = collapsible_margins_in_children.collapsed_through &&
-        pbm.padding_border_sums.block == Au::zero() &&
+        pbm.padding_border_sums.block.is_zero() &&
         block_size_is_zero_or_intrinsic(computed_block_size, containing_block) &&
         block_size_is_zero_or_intrinsic(style.min_block_size(), containing_block);
     block_margins_collapsed_with_children.collapsed_through = collapsed_through;
 
     let end_margin_can_collapse_with_children = collapsed_through ||
-        (pbm.padding.block_end == Au::zero() &&
-            pbm.border.block_end == Au::zero() &&
+        (pbm.padding.block_end.is_zero() &&
+            pbm.border.block_end.is_zero() &&
             !containing_block_for_children.size.block.is_definite());
     if end_margin_can_collapse_with_children {
         block_margins_collapsed_with_children

components/layout_2020/table/layout.rs

@@ -960,7 +960,7 @@ impl<'a> TableLayout<'a> {
             .clone()
             .map(max_content_sum)
             .fold(Au::zero(), |a, b| a + b);
-        if total_max_content_width != Au::zero() {
+        if !total_max_content_width.is_zero() {
             for column_index in unconstrained_max_content_columns {
                 column_sizes[column_index] += extra_inline_size.scale_by(
                     columns[column_index].content_sizes.max_content.to_f32_px() /
@@ -1005,7 +1005,7 @@ impl<'a> TableLayout<'a> {
             .clone()
             .map(max_content_sum)
             .fold(Au::zero(), |a, b| a + b);
-        if total_max_content_width != Au::zero() {
+        if !total_max_content_width.is_zero() {
             for column_index in constrained_max_content_columns {
                 column_sizes[column_index] += extra_inline_size.scale_by(
                     columns[column_index].content_sizes.max_content.to_f32_px() /

components/layout_2020/tests/floats.rs

@@ -11,12 +11,12 @@ use std::sync::{Mutex, MutexGuard};
 use std::{thread, u32};
 
 use app_units::Au;
-use euclid::num::Zero;
 use layout_2020::flow::float::{
     Clear, ContainingBlockPositionInfo, FloatBand, FloatBandNode, FloatBandTree, FloatContext,
     FloatSide, PlacementInfo,
 };
 use layout_2020::geom::{LogicalRect, LogicalVec2};
+use num_traits::identities::Zero;
 use quickcheck::{Arbitrary, Gen};
 
 static PANIC_HOOK_MUTEX: Mutex<()> = Mutex::new(());
@@ -559,7 +559,7 @@ fn check_floats_rule_3(placement: &FloatPlacement) {
             // Where the top of `b` should probably be 32px per Rule 3, but unless this distinction
             // is made the top of `b` could legally be 0px.
             if this_float.origin.block >= other_float.rect().max_block_position() ||
-                (this_float.info.size.block == Au::zero() &&
+                (this_float.info.size.block.is_zero() &&
                     this_float.rect().max_block_position() < other_float.origin.block) ||
                 (this_float.info.size.block > Au::zero() &&
                     this_float.rect().max_block_position() <= other_float.origin.block)
@@ -729,7 +729,7 @@ fn check_floats_rule_10(placement: &FloatPlacement) {
             // Where the top of `b` should probably be 32px per Rule 3, but unless this distinction
             // is made the top of `b` could legally be 0px.
             if this_float.origin.block >= other_float.rect().max_block_position() ||
-                (this_float.info.size.block == Au::zero() &&
+                (this_float.info.size.block.is_zero() &&
                     this_float.rect().max_block_position() < other_float.origin.block) ||
                 (this_float.info.size.block > Au::zero() &&
                     this_float.rect().max_block_position() <= other_float.origin.block)