Auto merge of #13848 - mrobinson:remove-layers, r=glennw

Remove concept of Layers from Servo

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- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [x] These changes do not require tests because this PR should not change behavior.

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Layers were a feature of the legacy drawing path. If we re-add them at
some point, it probably makes more sense to make them a product of
display list inspection.

This change also remove a bunch of dead painting code.

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components/script_layout_interface/message.rs

@@ -6,7 +6,7 @@ use {OpaqueStyleAndLayoutData, TrustedNodeAddress};
 use app_units::Au;
 use euclid::point::Point2D;
 use euclid::rect::Rect;
-use gfx_traits::{Epoch, LayerId};
+use gfx_traits::Epoch;
 use ipc_channel::ipc::{IpcReceiver, IpcSender};
 use msg::constellation_msg::PipelineId;
 use net_traits::image_cache_thread::ImageCacheThread;
@@ -48,10 +48,6 @@ pub enum Msg {
     /// Requests that the layout thread reflow with a newly-loaded Web font.
     ReflowWithNewlyLoadedWebFont,
 
-    /// Updates the layout visible rects, affecting the area that display lists will be constructed
-    /// for.
-    SetVisibleRects(Vec<(LayerId, Rect<Au>)>),
-
     /// Destroys layout data associated with a DOM node.
     ///
     /// TODO(pcwalton): Maybe think about batching to avoid message traffic.
@@ -99,7 +95,6 @@ pub enum ReflowQueryType {
     NodeOverflowQuery(TrustedNodeAddress),
     HitTestQuery(Point2D<f32>, Point2D<f32>, bool),
     NodeGeometryQuery(TrustedNodeAddress),
-    NodeLayerIdQuery(TrustedNodeAddress),
     NodeScrollGeometryQuery(TrustedNodeAddress),
     ResolvedStyleQuery(TrustedNodeAddress, Option<PseudoElement>, Atom),
     OffsetParentQuery(TrustedNodeAddress),

components/script_layout_interface/rpc.rs

@@ -5,7 +5,6 @@
 use app_units::Au;
 use euclid::point::Point2D;
 use euclid::rect::Rect;
-use gfx_traits::LayerId;
 use script_traits::UntrustedNodeAddress;
 use style::properties::longhands::{margin_top, margin_right, margin_bottom, margin_left, overflow_x};
 
@@ -28,8 +27,6 @@ pub trait LayoutRPC {
     fn node_overflow(&self) -> NodeOverflowResponse;
     /// Requests the scroll geometry of this node. Used by APIs such as `scrollTop`.
     fn node_scroll_area(&self) -> NodeGeometryResponse;
-    /// Requests the layer id of this node. Used by APIs such as `scrollTop`
-    fn node_layer_id(&self) -> NodeLayerIdResponse;
     /// Requests the node containing the point of interest
     fn hit_test(&self) -> HitTestResponse;
     /// Query layout for the resolved value of a given CSS property
@@ -51,10 +48,6 @@ pub struct NodeGeometryResponse {
 
 pub struct NodeOverflowResponse(pub Option<Point2D<overflow_x::computed_value::T>>);
 
-pub struct NodeLayerIdResponse {
-    pub layer_id: LayerId,
-}
-
 pub struct HitTestResponse {
     pub node_address: Option<UntrustedNodeAddress>,
 }

components/script_layout_interface/wrapper_traits.rs

@@ -8,7 +8,7 @@ use HTMLCanvasData;
 use LayoutNodeType;
 use OpaqueStyleAndLayoutData;
 use SVGSVGData;
-use gfx_traits::{ByteIndex, LayerId, LayerType};
+use gfx_traits::ByteIndex;
 use msg::constellation_msg::PipelineId;
 use range::Range;
 use restyle_damage::RestyleDamage;
@@ -377,21 +377,6 @@ pub trait ThreadSafeLayoutNode: Clone + Copy + NodeInfo + PartialEq + Sized {
 
     fn get_colspan(&self) -> u32;
 
-    fn layer_id(&self) -> LayerId {
-        let layer_type = match self.get_pseudo_element_type() {
-            PseudoElementType::Normal => LayerType::FragmentBody,
-            PseudoElementType::Before(_) => LayerType::BeforePseudoContent,
-            PseudoElementType::After(_) => LayerType::AfterPseudoContent,
-            PseudoElementType::DetailsSummary(_) => LayerType::FragmentBody,
-            PseudoElementType::DetailsContent(_) => LayerType::FragmentBody,
-        };
-        LayerId::new_of_type(layer_type, self.opaque().id() as usize)
-    }
-
-    fn layer_id_for_overflow_scroll(&self) -> LayerId {
-        LayerId::new_of_type(LayerType::OverflowScroll, self.opaque().id() as usize)
-    }
-
     fn get_style_data(&self) -> Option<&AtomicRefCell<PersistentStyleData>>;
 }