script: Make the ImageCacheTask use IPC.

This necessitated getting rid of the boxed trait object that was being
be passed between the script task and the image cache task.

components/script/dom/canvasrenderingcontext2d.rs

@@ -28,7 +28,6 @@ use euclid::matrix2d::Matrix2D;
 use euclid::point::Point2D;
 use euclid::rect::Rect;
 use euclid::size::Size2D;
-use ipc_channel::ipc;
 
 use canvas_traits::{CanvasMsg, Canvas2dMsg, CanvasCommonMsg};
 use canvas_traits::{FillOrStrokeStyle, LinearGradientStyle, RadialGradientStyle, RepetitionStyle};
@@ -38,7 +37,7 @@ use msg::constellation_msg::Msg as ConstellationMsg;
 use net_traits::image_cache_task::{ImageCacheChan, ImageResponse};
 use net_traits::image::base::PixelFormat;
 
-use ipc_channel::ipc::IpcSender;
+use ipc_channel::ipc::{self, IpcSender};
 use num::{Float, ToPrimitive};
 use std::borrow::ToOwned;
 use std::cell::RefCell;
@@ -341,7 +340,7 @@ impl CanvasRenderingContext2D {
         let window = window_from_node(canvas.r());
         let window = window.r();
         let image_cache = window.image_cache_task();
-        let (response_chan, response_port) = channel();
+        let (response_chan, response_port) = ipc::channel().unwrap();
         image_cache.request_image(url, ImageCacheChan(response_chan), None);
         let result = response_port.recv().unwrap();
         result.image_response

components/script/dom/htmlimageelement.rs

@@ -23,9 +23,12 @@ use dom::htmlelement::{HTMLElement, HTMLElementTypeId};
 use dom::node::{document_from_node, Node, NodeTypeId, NodeHelpers, NodeDamage, window_from_node};
 use dom::virtualmethods::VirtualMethods;
 use dom::window::WindowHelpers;
+use script_task::{Runnable, ScriptChan, ScriptMsg};
 use util::str::DOMString;
 use string_cache::Atom;
 
+use ipc_channel::ipc;
+use ipc_channel::router::ROUTER;
 use net_traits::image::base::Image;
 use net_traits::image_cache_task::{ImageResponder, ImageResponse};
 use url::{Url, UrlParser};
@@ -62,27 +65,27 @@ trait PrivateHTMLImageElementHelpers {
     fn update_image(self, value: Option<(DOMString, &Url)>);
 }
 
-/// This is passed to the image cache when the src attribute
-/// changes. It is returned via a message to the script task,
-/// which marks the element as dirty and triggers a reflow.
-struct Responder {
+struct ImageResponseHandlerRunnable {
     element: Trusted<HTMLImageElement>,
+    image: ImageResponse,
 }
 
-impl Responder {
-    fn new(element: Trusted<HTMLImageElement>) -> Responder {
-        Responder {
-            element: element
+impl ImageResponseHandlerRunnable {
+    fn new(element: Trusted<HTMLImageElement>, image: ImageResponse)
+           -> ImageResponseHandlerRunnable {
+        ImageResponseHandlerRunnable {
+            element: element,
+            image: image,
         }
     }
 }
 
-impl ImageResponder for Responder {
-    fn respond(&self, image: ImageResponse) {
+impl Runnable for ImageResponseHandlerRunnable {
+    fn handler(self: Box<Self>) {
         // Update the image field
         let element = self.element.root();
         let element_ref = element.r();
-        *element_ref.image.borrow_mut() = match image {
+        *element_ref.image.borrow_mut() = match self.image {
             ImageResponse::Loaded(image) | ImageResponse::PlaceholderLoaded(image) => {
                 Some(image)
             }
@@ -130,8 +133,20 @@ impl<'a> PrivateHTMLImageElementHelpers for &'a HTMLImageElement {
                 *self.url.borrow_mut() = Some(img_url.clone());
 
                 let trusted_node = Trusted::new(window.get_cx(), self, window.script_chan());
-                let responder = box Responder::new(trusted_node);
-                image_cache.request_image(img_url, window.image_cache_chan(), Some(responder));
+                let (responder_sender, responder_receiver) = ipc::channel().unwrap();
+                let script_chan = window.script_chan();
+                ROUTER.add_route(responder_receiver.to_opaque(), box move |message| {
+                    // Return the image via a message to the script task, which marks the element
+                    // as dirty and triggers a reflow.
+                    let image_response = message.to().unwrap();
+                    script_chan.send(ScriptMsg::RunnableMsg(box ImageResponseHandlerRunnable::new(
+                                trusted_node.clone(),
+                                image_response))).unwrap();
+                });
+
+                image_cache.request_image(img_url,
+                                          window.image_cache_chan(),
+                                          Some(ImageResponder::new(responder_sender)));
             }
         }
     }