Remove old rendering backend.

This removes paint threads, rust-layers dependency, and changes
optional webrender types to be required.

The use_webrender option has been removed, however I've left
the "-w" command line option in place so that wpt
runner can continue to pass that. Once it's removed from there
we can also remove the -w option.

Once this stage is complete, it should be fine to change the
display list building code to generate webrender display
lists directly and avoid the conversion step.

components/script/dom/canvasrenderingcontext2d.rs

@@ -5,7 +5,7 @@
 use canvas_traits::{Canvas2dMsg, CanvasCommonMsg, CanvasMsg};
 use canvas_traits::{CompositionOrBlending, FillOrStrokeStyle, FillRule};
 use canvas_traits::{LineCapStyle, LineJoinStyle, LinearGradientStyle};
-use canvas_traits::{RadialGradientStyle, RepetitionStyle, byte_swap, byte_swap_and_premultiply};
+use canvas_traits::{RadialGradientStyle, RepetitionStyle, byte_swap_and_premultiply};
 use cssparser::{Parser, RGBA};
 use cssparser::Color as CSSColor;
 use dom::bindings::cell::DOMRefCell;
@@ -47,7 +47,6 @@ use std::cell::Cell;
 use std::str::FromStr;
 use unpremultiplytable::UNPREMULTIPLY_TABLE;
 use url::Url;
-use util::opts;
 
 #[must_root]
 #[derive(JSTraceable, Clone, HeapSizeOf)]
@@ -297,14 +296,7 @@ impl CanvasRenderingContext2D {
                     Some((mut data, size)) => {
                         // Pixels come from cache in BGRA order and drawImage expects RGBA so we
                         // have to swap the color values
-                        if opts::get().use_webrender {
-                            // Webrender doesn't pre-multiply alpha when decoding
-                            // images, but canvas expects the images to be
-                            // pre-multiplied alpha.
-                            byte_swap_and_premultiply(&mut data);
-                        } else {
-                            byte_swap(&mut data);
-                        }
+                        byte_swap_and_premultiply(&mut data);
                         let size = Size2D::new(size.width as f64, size.height as f64);
                         (data, size)
                     },

components/script/dom/window.rs

@@ -1220,42 +1220,20 @@ impl Window {
     }
 
     pub fn scroll_offset_query(&self, node: &Node) -> Point2D<f32> {
-        // WebRender always keeps the scroll offsets up to date and stored here in the window. So,
-        // if WR is in use, all we need to do is to check our list of scroll offsets and return the
-        // result.
-        if opts::get().use_webrender {
-            let mut node = Root::from_ref(node);
-            loop {
-                if let Some(scroll_offset) = self.scroll_offsets
-                                                 .borrow()
-                                                 .get(&node.to_untrusted_node_address()) {
-                    return *scroll_offset
-                }
-                node = match node.GetParentNode() {
-                    Some(node) => node,
-                    None => break,
-                }
+        let mut node = Root::from_ref(node);
+        loop {
+            if let Some(scroll_offset) = self.scroll_offsets
+                                             .borrow()
+                                             .get(&node.to_untrusted_node_address()) {
+                return *scroll_offset
+            }
+            node = match node.GetParentNode() {
+                Some(node) => node,
+                None => break,
             }
-            let offset = self.current_viewport.get().origin;
-            return Point2D::new(offset.x.to_f32_px(), offset.y.to_f32_px())
         }
-
-        let node = node.to_trusted_node_address();
-        if !self.reflow(ReflowGoal::ForScriptQuery,
-                        ReflowQueryType::NodeLayerIdQuery(node),
-                        ReflowReason::Query) {
-            return Point2D::zero();
-        }
-
-        let layer_id = self.layout_rpc.node_layer_id().layer_id;
-
-        let (send, recv) = ipc::channel::<Point2D<f32>>().unwrap();
-        let global_scope = self.upcast::<GlobalScope>();
-        global_scope
-            .constellation_chan()
-            .send(ConstellationMsg::GetScrollOffset(global_scope.pipeline_id(), layer_id, send))
-            .unwrap();
-        recv.recv().unwrap_or(Point2D::zero())
+        let offset = self.current_viewport.get().origin;
+        Point2D::new(offset.x.to_f32_px(), offset.y.to_f32_px())
     }
 
     // https://drafts.csswg.org/cssom-view/#dom-element-scroll

components/script/script_thread.rs

@@ -1143,7 +1143,6 @@ impl ScriptThread {
             new_pipeline_id,
             frame_type,
             load_data,
-            paint_chan,
             pipeline_port,
             layout_to_constellation_chan,
             content_process_shutdown_chan,
@@ -1160,7 +1159,6 @@ impl ScriptThread {
             layout_pair: layout_pair,
             pipeline_port: pipeline_port,
             constellation_chan: layout_to_constellation_chan,
-            paint_chan: paint_chan,
             script_chan: self.control_chan.clone(),
             image_cache_thread: self.image_cache_thread.clone(),
             content_process_shutdown_chan: content_process_shutdown_chan,