Clean up of script timer code.

The code was split into the following two abstractions.
 - OneshotTimers can be used to schedule arbitrary oneshot timers, such
   as XHR-Timeouts.
 - JsTimers (`setTimeout` and `setInterval`) which use OneshotTimers to
   schedule individual callbacks.

With this change the implementation (of JsTimers in particular) is in
much closer alignment with the specification.

components/script/dom/workerglobalscope.rs

@@ -30,7 +30,7 @@ use std::cell::Cell;
 use std::default::Default;
 use std::rc::Rc;
 use std::sync::mpsc::Receiver;
-use timers::{ActiveTimers, IsInterval, ScheduledCallback, TimerCallback, TimerHandle};
+use timers::{IsInterval, OneshotTimerCallback, OneshotTimerHandle, OneshotTimers, TimerCallback};
 use url::Url;
 use util::str::DOMString;
 
@@ -64,7 +64,7 @@ pub struct WorkerGlobalScope {
     navigator: MutNullableHeap<JS<WorkerNavigator>>,
     console: MutNullableHeap<JS<Console>>,
     crypto: MutNullableHeap<JS<Crypto>>,
-    timers: ActiveTimers,
+    timers: OneshotTimers,
     #[ignore_heap_size_of = "Defined in std"]
     mem_profiler_chan: mem::ProfilerChan,
     #[ignore_heap_size_of = "Defined in ipc-channel"]
@@ -98,6 +98,7 @@ impl WorkerGlobalScope {
                          from_devtools_receiver: Receiver<DevtoolScriptControlMsg>,
                          timer_event_chan: IpcSender<TimerEvent>)
                          -> WorkerGlobalScope {
+
         WorkerGlobalScope {
             eventtarget: EventTarget::new_inherited(),
             next_worker_id: Cell::new(WorkerId(0)),
@@ -109,7 +110,7 @@ impl WorkerGlobalScope {
             navigator: Default::default(),
             console: Default::default(),
             crypto: Default::default(),
-            timers: ActiveTimers::new(timer_event_chan, init.scheduler_chan.clone()),
+            timers: OneshotTimers::new(timer_event_chan, init.scheduler_chan.clone()),
             mem_profiler_chan: init.mem_profiler_chan,
             to_devtools_sender: init.to_devtools_sender,
             from_devtools_sender: init.from_devtools_sender,
@@ -144,13 +145,13 @@ impl WorkerGlobalScope {
         self.scheduler_chan.clone()
     }
 
-    pub fn schedule_callback(&self, callback: Box<ScheduledCallback>, duration: MsDuration) -> TimerHandle {
+    pub fn schedule_callback(&self, callback: OneshotTimerCallback, duration: MsDuration) -> OneshotTimerHandle {
         self.timers.schedule_callback(callback,
                                       duration,
                                       TimerSource::FromWorker)
     }
 
-    pub fn unschedule_callback(&self, handle: TimerHandle) {
+    pub fn unschedule_callback(&self, handle: OneshotTimerHandle) {
         self.timers.unschedule_callback(handle);
     }
 
@@ -250,7 +251,8 @@ impl WorkerGlobalScopeMethods for WorkerGlobalScope {
 
     // https://html.spec.whatwg.org/multipage/#dom-windowtimers-setinterval
     fn SetTimeout(&self, _cx: *mut JSContext, callback: Rc<Function>, timeout: i32, args: Vec<HandleValue>) -> i32 {
-        self.timers.set_timeout_or_interval(TimerCallback::FunctionTimerCallback(callback),
+        self.timers.set_timeout_or_interval(GlobalRef::Worker(self),
+                                            TimerCallback::FunctionTimerCallback(callback),
                                             args,
                                             timeout,
                                             IsInterval::NonInterval,
@@ -259,7 +261,8 @@ impl WorkerGlobalScopeMethods for WorkerGlobalScope {
 
     // https://html.spec.whatwg.org/multipage/#dom-windowtimers-setinterval
     fn SetTimeout_(&self, _cx: *mut JSContext, callback: DOMString, timeout: i32, args: Vec<HandleValue>) -> i32 {
-        self.timers.set_timeout_or_interval(TimerCallback::StringTimerCallback(callback),
+        self.timers.set_timeout_or_interval(GlobalRef::Worker(self),
+                                            TimerCallback::StringTimerCallback(callback),
                                             args,
                                             timeout,
                                             IsInterval::NonInterval,
@@ -268,12 +271,13 @@ impl WorkerGlobalScopeMethods for WorkerGlobalScope {
 
     // https://html.spec.whatwg.org/multipage/#dom-windowtimers-clearinterval
     fn ClearTimeout(&self, handle: i32) {
-        self.timers.clear_timeout_or_interval(handle);
+        self.timers.clear_timeout_or_interval(GlobalRef::Worker(self), handle);
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-windowtimers-setinterval
     fn SetInterval(&self, _cx: *mut JSContext, callback: Rc<Function>, timeout: i32, args: Vec<HandleValue>) -> i32 {
-        self.timers.set_timeout_or_interval(TimerCallback::FunctionTimerCallback(callback),
+        self.timers.set_timeout_or_interval(GlobalRef::Worker(self),
+                                            TimerCallback::FunctionTimerCallback(callback),
                                             args,
                                             timeout,
                                             IsInterval::Interval,
@@ -282,7 +286,8 @@ impl WorkerGlobalScopeMethods for WorkerGlobalScope {
 
     // https://html.spec.whatwg.org/multipage/#dom-windowtimers-setinterval
     fn SetInterval_(&self, _cx: *mut JSContext, callback: DOMString, timeout: i32, args: Vec<HandleValue>) -> i32 {
-        self.timers.set_timeout_or_interval(TimerCallback::StringTimerCallback(callback),
+        self.timers.set_timeout_or_interval(GlobalRef::Worker(self),
+                                            TimerCallback::StringTimerCallback(callback),
                                             args,
                                             timeout,
                                             IsInterval::Interval,