Remove DropSource from mio

I'm... not sure if it does anything any more as a `ReadinessStream` isn't
clone-able nor is it split. As a result, I don't think we need it.

src/event_loop.rs

@@ -232,6 +232,7 @@ impl Loop {
     fn deschedule(&self, token: usize) {
         let mut dispatch = self.dispatch.borrow_mut();
         dispatch.get_mut(token).unwrap();
+        // TODO: was... this supposed to do something?
     }
 
     fn consume_queue(&self) {

src/readiness_stream.rs

@@ -1,41 +1,10 @@
 use std::io;
-use std::sync::Arc;
 
 use futures::stream::Stream;
 use futures::{Future, Task, Poll};
 use futures_io::{Ready, IoFuture};
 
 use event_loop::{IoSource, LoopHandle};
-use readiness_stream::drop_source::DropSource;
-
-
-// TODO: figure out a nicer way to factor this
-mod drop_source {
-    use event_loop::LoopHandle;
-
-    pub struct DropSource {
-        token: usize,
-        loop_handle: LoopHandle,
-    }
-
-    impl DropSource {
-        pub fn new(token: usize, loop_handle: LoopHandle) -> DropSource {
-            DropSource {
-                token: token,
-                loop_handle: loop_handle,
-            }
-        }
-    }
-
-    // Safe because no public access exposed to LoopHandle; only used in drop
-    unsafe impl Sync for DropSource {}
-
-    impl Drop for DropSource {
-        fn drop(&mut self) {
-            self.loop_handle.drop_source(self.token)
-        }
-    }
-}
 
 /// A concrete implementation of a stream of readiness notifications for I/O
 /// objects that originates from an event loop.
@@ -54,7 +23,6 @@ pub struct ReadinessStream {
     io_token: usize,
     loop_handle: LoopHandle,
     source: IoSource,
-    _drop_source: Arc<DropSource>,
 }
 
 impl ReadinessStream {
@@ -66,12 +34,10 @@ impl ReadinessStream {
     pub fn new(loop_handle: LoopHandle, source: IoSource)
                -> Box<IoFuture<ReadinessStream>> {
         loop_handle.add_source(source.clone()).map(|token| {
-            let drop_source = Arc::new(DropSource::new(token, loop_handle.clone()));
             ReadinessStream {
                 io_token: token,
                 source: source,
                 loop_handle: loop_handle,
-                _drop_source: drop_source,
             }
         }).boxed()
     }
@@ -95,6 +61,6 @@ impl Stream for ReadinessStream {
 
 impl Drop for ReadinessStream {
     fn drop(&mut self) {
-        self.loop_handle.deschedule(self.io_token)
+        self.loop_handle.drop_source(self.io_token)
     }
 }