Handle removed pipelines.

webrender/src/frame.rs

@@ -27,6 +27,7 @@ use renderer::PipelineInfo;
 use render_backend::{SceneRequest, BuiltScene};
 
 use std::sync::Arc;
+use std::mem::replace;
 
 #[derive(Copy, Clone, PartialEq, PartialOrd, Debug, Eq, Ord)]
 #[cfg_attr(feature = "capture", derive(Serialize))]
@@ -1175,9 +1176,9 @@ impl FrameContext {
     // This will soon replace the method above and move somewhere else.
     pub fn create_frame_builder_async(
         config: &FrameBuilderConfig,
-        request: SceneRequest,
+        mut request: SceneRequest,
     ) -> BuiltScene {
-        let scene = &request.scene;
+        let scene = &mut request.scene;
         let inner_rect = request.view.inner_rect;
         let window_size = request.view.window_size;
         let device_pixel_scale = request.view.accumulated_scale_factor();
@@ -1246,6 +1247,7 @@ impl FrameContext {
             frame_builder,
             clip_scroll_tree,
             pipeline_epoch_map,
+            removed_pipelines: replace(&mut scene.removed_pipelines, Vec::new()),
             document_id: request.document_id,
             render: request.render,
         }

webrender/src/render_backend.rs

@@ -566,9 +566,10 @@ impl RenderBackend {
         loop {
             profile_scope!("handle_msg");
 
-            while let Ok(msg) = self.scene_rx.try_recv() {
+            while let Ok(mut msg) = self.scene_rx.try_recv() {
                 if let Some(doc) = self.documents.get_mut(&msg.document_id) {
                     doc.frame_builder = Some(msg.frame_builder);
+                    doc.removed_pipelines.extend(msg.removed_pipelines.drain(..));
                     doc.frame_ctx.new_async_scene_ready(
                         msg.clip_scroll_tree,
                         msg.pipeline_epoch_map,
@@ -1154,6 +1155,7 @@ pub struct BuiltScene {
     pub frame_builder: FrameBuilder,
     pub clip_scroll_tree: ClipScrollTree,
     pub pipeline_epoch_map: FastHashMap<PipelineId, Epoch>,
+    pub removed_pipelines: Vec<PipelineId>,
     pub document_id: DocumentId,
     pub render: bool,
 }