Auto merge of #16510 - mrobinson:establishes-3d-context, r=jdm

Remove StackingContext::establishes_3d_context

This member is now unused since WebRender is the only display backend.

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components/gfx/display_list/mod.rs

@@ -373,9 +373,6 @@ pub struct StackingContext {
     /// The perspective matrix to be applied to children.
     pub perspective: Option<Matrix4D<f32>>,
 
-    /// Whether this stacking context creates a new 3d rendering context.
-    pub establishes_3d_context: bool,
-
     /// The scroll policy of this layer.
     pub scroll_policy: ScrollPolicy,
 
@@ -395,7 +392,6 @@ impl StackingContext {
                blend_mode: mix_blend_mode::T,
                transform: Option<Matrix4D<f32>>,
                perspective: Option<Matrix4D<f32>>,
-               establishes_3d_context: bool,
                scroll_policy: ScrollPolicy,
                parent_scroll_id: ScrollRootId)
                -> StackingContext {
@@ -409,7 +405,6 @@ impl StackingContext {
             blend_mode: blend_mode,
             transform: transform,
             perspective: perspective,
-            establishes_3d_context: establishes_3d_context,
             scroll_policy: scroll_policy,
             parent_scroll_id: parent_scroll_id,
         }
@@ -426,7 +421,6 @@ impl StackingContext {
                              mix_blend_mode::T::normal,
                              None,
                              None,
-                             true,
                              ScrollPolicy::Scrollable,
                              ScrollRootId::root())
     }

components/layout/display_list_builder.rs

@@ -47,9 +47,8 @@ use std::default::Default;
 use std::mem;
 use std::sync::Arc;
 use style::computed_values::{background_attachment, background_clip, background_origin};
-use style::computed_values::{background_repeat, background_size, border_style};
-use style::computed_values::{cursor, image_rendering, overflow_x};
-use style::computed_values::{pointer_events, position, transform_style, visibility};
+use style::computed_values::{background_repeat, background_size, border_style, cursor};
+use style::computed_values::{image_rendering, overflow_x, pointer_events, position, visibility};
 use style::computed_values::filter::Filter;
 use style::computed_values::text_shadow::TextShadow;
 use style::logical_geometry::{LogicalPoint, LogicalRect, LogicalSize, WritingMode};
@@ -58,8 +57,8 @@ use style::properties::longhands::border_image_repeat::computed_value::RepeatKey
 use style::properties::style_structs;
 use style::servo::restyle_damage::REPAINT;
 use style::values::{Either, RGBA, computed};
-use style::values::computed::{AngleOrCorner, Gradient, GradientKind, LengthOrPercentage, LengthOrPercentageOrAuto};
-use style::values::computed::NumberOrPercentage;
+use style::values::computed::{AngleOrCorner, Gradient, GradientKind, LengthOrPercentage};
+use style::values::computed::{LengthOrPercentageOrAuto, NumberOrPercentage};
 use style::values::specified::{HorizontalDirection, VerticalDirection};
 use style_traits::CSSPixel;
 use style_traits::cursor::Cursor;
@@ -1685,9 +1684,6 @@ impl FragmentDisplayListBuilding for Fragment {
             filters.push(Filter::Opacity(effects.opacity))
         }
 
-        let transform_style = self.style().get_used_transform_style();
-        let establishes_3d_context = transform_style == transform_style::T::flat;
-
         let context_type = match mode {
             StackingContextCreationMode::PseudoFloat => StackingContextType::PseudoFloat,
             StackingContextCreationMode::PseudoPositioned => StackingContextType::PseudoPositioned,
@@ -1703,7 +1699,6 @@ impl FragmentDisplayListBuilding for Fragment {
                              self.style().get_effects().mix_blend_mode,
                              self.transform_matrix(&border_box),
                              self.perspective_matrix(&border_box),
-                             establishes_3d_context,
                              scroll_policy,
                              parent_scroll_id)
     }