diff --git a/components/script/dom/bindings/error.rs b/components/script/dom/bindings/error.rs
index 961ba959b8948..4cfdd3a066310 100644
--- a/components/script/dom/bindings/error.rs
+++ b/components/script/dom/bindings/error.rs
@@ -19,7 +19,7 @@ use libc;
 use std::ptr;
 
 /// DOM exceptions that can be thrown by a native DOM method.
-#[deriving(Show)]
+#[deriving(Show, Clone)]
 pub enum Error {
     IndexSize,
     FailureUnknown,
diff --git a/components/script/dom/dedicatedworkerglobalscope.rs b/components/script/dom/dedicatedworkerglobalscope.rs
index f29691afcf6b0..9b9b08704ec34 100644
--- a/components/script/dom/dedicatedworkerglobalscope.rs
+++ b/components/script/dom/dedicatedworkerglobalscope.rs
@@ -17,7 +17,6 @@ use dom::messageevent::MessageEvent;
 use dom::worker::{Worker, TrustedWorkerAddress};
 use dom::workerglobalscope::{WorkerGlobalScope, WorkerGlobalScopeHelpers};
 use dom::workerglobalscope::WorkerGlobalScopeTypeId;
-use dom::xmlhttprequest::XMLHttpRequest;
 use script_task::{ScriptTask, ScriptChan, ScriptMsg, TimerSource};
 use script_task::StackRootTLS;
 
@@ -131,11 +130,8 @@ impl DedicatedWorkerGlobalScope {
                         MessageEvent::dispatch_jsval(target, GlobalRef::Worker(scope), message);
                         global.delayed_release_worker();
                     },
-                    Ok(ScriptMsg::XHRProgress(addr, progress)) => {
-                        XMLHttpRequest::handle_progress(addr, progress)
-                    },
-                    Ok(ScriptMsg::XHRRelease(addr)) => {
-                        XMLHttpRequest::handle_release(addr)
+                    Ok(ScriptMsg::RunnableMsg(runnable)) => {
+                        runnable.handler()
                     },
                     Ok(ScriptMsg::WorkerPostMessage(addr, data, nbytes)) => {
                         Worker::handle_message(addr, data, nbytes);
diff --git a/components/script/dom/xmlhttprequest.rs b/components/script/dom/xmlhttprequest.rs
index cd6d185076386..21495b9f4b38a 100644
--- a/components/script/dom/xmlhttprequest.rs
+++ b/components/script/dom/xmlhttprequest.rs
@@ -25,7 +25,7 @@ use dom::urlsearchparams::URLSearchParamsHelpers;
 use dom::xmlhttprequesteventtarget::XMLHttpRequestEventTarget;
 use dom::xmlhttprequesteventtarget::XMLHttpRequestEventTargetTypeId;
 use dom::xmlhttprequestupload::XMLHttpRequestUpload;
-use script_task::{ScriptChan, ScriptMsg};
+use script_task::{ScriptChan, ScriptMsg, Runnable};
 
 use encoding::all::UTF_8;
 use encoding::label::encoding_from_whatwg_label;
@@ -73,10 +73,37 @@ enum XMLHttpRequestState {
     XHRDone = 4, // So as not to conflict with the ProgressMsg `Done`
 }
 
-#[deriving(PartialEq)]
+struct XHRReleaseHandler(TrustedXHRAddress);
+
+impl Runnable for XHRReleaseHandler {
+    fn handler(&self) {
+        let XHRReleaseHandler(addr) = *self;
+        XMLHttpRequest::handle_release(addr);
+    }
+}
+
+struct XHRProgressHandler {
+    addr: TrustedXHRAddress,
+    progress: XHRProgress,
+}
+
+impl XHRProgressHandler {
+    fn new(addr: TrustedXHRAddress, progress: XHRProgress) -> XHRProgressHandler {
+        XHRProgressHandler { addr: addr, progress: progress }
+    }
+}
+
+impl Runnable for XHRProgressHandler {
+    fn handler(&self) {
+        XMLHttpRequest::handle_progress(self.addr, self.progress.clone());
+    }
+}
+
+#[deriving(PartialEq, Clone)]
 #[jstraceable]
 pub struct GenerationId(uint);
 
+#[deriving(Clone)]
 pub enum XHRProgress {
     /// Notify that headers have been received
     HeadersReceived(GenerationId, Option<Headers>, Option<RawStatus>),
@@ -208,7 +235,7 @@ impl XMLHttpRequest {
                 },
                 SyncOrAsync::Async(addr, script_chan) => {
                     let ScriptChan(ref chan) = *script_chan;
-                    chan.send(ScriptMsg::XHRProgress(addr, msg));
+                    chan.send(ScriptMsg::RunnableMsg(box XHRProgressHandler::new(addr, msg)));
                 }
             }
         }
@@ -609,7 +636,7 @@ impl<'a> XMLHttpRequestMethods for JSRef<'a, XMLHttpRequest> {
             self.fetch_time.set(time::now().to_timespec().sec);
             let script_chan = global.root_ref().script_chan().clone();
             // Pin the object before launching the fetch task.
-            // The `ScriptMsg::XHRRelease` sent when the fetch task completes will
+            // The `ScriptMsg::RunnableMsg` sent when the fetch task completes will
             // unpin it. This is to ensure that the object will stay alive
             // as long as there are (possibly cancelled) inflight events queued up
             // in the script task's port
@@ -625,7 +652,7 @@ impl<'a> XMLHttpRequestMethods for JSRef<'a, XMLHttpRequest> {
                                               gen_id,
                                               start_port);
                 let ScriptChan(ref chan) = script_chan;
-                chan.send(ScriptMsg::XHRRelease(addr));
+                chan.send(ScriptMsg::RunnableMsg(box XHRReleaseHandler(addr)));
             });
             let timeout = self.timeout.get();
             if timeout > 0 {
diff --git a/components/script/script_task.rs b/components/script/script_task.rs
index 696d0e10f8fea..40d90e150cb7e 100644
--- a/components/script/script_task.rs
+++ b/components/script/script_task.rs
@@ -27,7 +27,6 @@ use dom::mouseevent::MouseEvent;
 use dom::node::{mod, Node, NodeHelpers, NodeDamage, NodeTypeId};
 use dom::window::{Window, WindowHelpers};
 use dom::worker::{Worker, TrustedWorkerAddress};
-use dom::xmlhttprequest::{TrustedXHRAddress, XMLHttpRequest, XHRProgress};
 use parse::html::{HTMLInput, parse_html};
 use layout_interface::{ScriptLayoutChan, LayoutChan, ReflowGoal, ReflowQueryType};
 use layout_interface;
@@ -87,6 +86,10 @@ pub enum TimerSource {
     FromWorker
 }
 
+pub trait Runnable {
+    fn handler(&self);
+}
+
 /// Messages used to control script event loops, such as ScriptTask and
 /// DedicatedWorkerGlobalScope.
 pub enum ScriptMsg {
@@ -106,10 +109,6 @@ pub enum ScriptMsg {
     /// Notifies the script that a window associated with a particular pipeline
     /// should be closed (only dispatched to ScriptTask).
     ExitWindow(PipelineId),
-    /// Notifies the script of progress on a fetch (dispatched to all tasks).
-    XHRProgress(TrustedXHRAddress, XHRProgress),
-    /// Releases one reference to the XHR object (dispatched to all tasks).
-    XHRRelease(TrustedXHRAddress),
     /// Message sent through Worker.postMessage (only dispatched to
     /// DedicatedWorkerGlobalScope).
     DOMMessage(*mut u64, size_t),
@@ -117,6 +116,8 @@ pub enum ScriptMsg {
     WorkerPostMessage(TrustedWorkerAddress, *mut u64, size_t),
     /// Releases one reference to the Worker object (dispatched to all tasks).
     WorkerRelease(TrustedWorkerAddress),
+    /// Generic message that encapsulates event handling.
+    RunnableMsg(Box<Runnable+Send>),
 }
 
 /// Encapsulates internal communication within the script task.
@@ -572,16 +573,14 @@ impl ScriptTask {
                 self.handle_navigate_msg(direction),
             ScriptMsg::ExitWindow(id) =>
                 self.handle_exit_window_msg(id),
-            ScriptMsg::XHRProgress(addr, progress) =>
-                XMLHttpRequest::handle_progress(addr, progress),
-            ScriptMsg::XHRRelease(addr) =>
-                XMLHttpRequest::handle_release(addr),
             ScriptMsg::DOMMessage(..) =>
                 panic!("unexpected message"),
             ScriptMsg::WorkerPostMessage(addr, data, nbytes) =>
                 Worker::handle_message(addr, data, nbytes),
             ScriptMsg::WorkerRelease(addr) =>
                 Worker::handle_release(addr),
+            ScriptMsg::RunnableMsg(runnable) =>
+                runnable.handler(),
         }
     }