Auto merge of #16891 - kvark:preserve3d, r=glennw,emilio

Using TransformStyle::Preserve3D

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The changes were reviewed previously as a part of WR update PRs, but then we decided to move them out.
r? @emilio

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- [ ] These changes fix #__ (github issue number if applicable).

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components/layout/fragment.rs

@@ -2470,7 +2470,10 @@ impl Fragment {
         if self.style().get_effects().mix_blend_mode != mix_blend_mode::T::normal {
             return true
         }
-        if self.style().get_box().transform.0.is_some() {
+
+        if self.style().get_box().transform.0.is_some() ||
+           self.style().get_box().transform_style == transform_style::T::preserve_3d ||
+           self.style().overrides_transform_style() {
             return true
         }
 
@@ -2485,13 +2488,6 @@ impl Fragment {
             return true
         }
 
-        match self.style().get_used_transform_style() {
-            transform_style::T::flat | transform_style::T::preserve_3d => {
-                return true
-            }
-            transform_style::T::auto => {}
-        }
-
         match (self.style().get_box().position,
                self.style().get_position().z_index,
                self.style().get_box().overflow_x,