Refactored image cache task - details below.

 * Simpler image cache API for clients to use.
 * Significantly fewer threads.
   * One thread for image cache task (multiplexes commands, decoder threads and async resource requests).
   * 4 threads for decoder worker tasks.
 * Removed ReflowEvent hacks in script and layout tasks.
   * Image elements pass a Trusted<T> to image cache, which is used to dirty nodes via script task. Previous use of Untrusted addresses was unsafe.
   * Image requests such as background-image on layout / paint threads trigger repaint only rather than full reflow.
 * Add reflow batching for when multiple images load quickly.
   * Reduces the number of paints loading wikipedia from ~95 to ~35.
 * Reasonably simple to add proper prefetch support in a follow up PR.
 * Async loaded images always construct Image fragments now, instead of generic.
   * Image fragments support the image not being present.
 * Simpler implementation of synchronous image loading for reftests.
 * Removed image holder.
 * image.onload support.
 * image NaturalWidth and NaturalHeight support.
 * Updated WPT expectations.

1 files changed, 5 insertions, 10 deletions

diff --git a/components/script/dom/canvasrenderingcontext2d.rs b/components/script/dom/canvasrenderingcontext2d.rs
index f6111739d8b..022b31dd055 100644
--- a/components/script/dom/canvasrenderingcontext2d.rs
+++ b/components/script/dom/canvasrenderingcontext2d.rs
@@ -33,7 +33,7 @@ use canvas::canvas_paint_task::{LinearGradientStyle, RadialGradientStyle};
 use canvas::canvas_paint_task::{LineCapStyle, LineJoinStyle, CompositionOrBlending};
 
 use net_traits::image::base::Image;
-use net_traits::image_cache_task::{ImageResponseMsg, Msg};
+use net_traits::image_cache_task::ImageCacheChan;
 use png::PixelsByColorType;
 
 use std::borrow::ToOwned;
@@ -275,16 +275,11 @@ impl CanvasRenderingContext2D {
         let canvas = self.canvas.root();
         let window = window_from_node(canvas.r()).root();
         let window = window.r();
-        let image_cache_task = window.image_cache_task().clone();
-        image_cache_task.send(Msg::Prefetch(url.clone()));
-        image_cache_task.send(Msg::Decode(url.clone()));
+        let image_cache = window.image_cache_task();
         let (response_chan, response_port) = channel();
-        image_cache_task.send(Msg::WaitForImage(url, response_chan));
-        match response_port.recv().unwrap() {
-           ImageResponseMsg::ImageReady(image) => Some(image),
-           ImageResponseMsg::ImageFailed => None,
-           _ => panic!("Image Cache: Unknown Result")
-         }
+        image_cache.request_image(url, ImageCacheChan(response_chan), None);
+        let result = response_port.recv().unwrap();
+        result.image
     }
 
     fn create_drawable_rect(&self, x: f64, y: f64, w: f64, h: f64) -> Option<Rect<f32>> {