Implement stdweb backend for web platform

src/platform_impl/web/stdweb/timeout.rs

@@ -0,0 +1,25 @@
+use std::time::Duration;
+use stdweb::web::{window, IWindowOrWorker, TimeoutHandle};
+
+#[derive(Debug)]
+pub struct Timeout {
+    handle: TimeoutHandle,
+}
+
+impl Timeout {
+    pub fn new<F>(f: F, duration: Duration) -> Timeout
+    where
+        F: 'static + FnMut(),
+    {
+        Timeout {
+            handle: window().set_clearable_timeout(f, duration.as_millis() as u32),
+        }
+    }
+}
+
+impl Drop for Timeout {
+    fn drop(&mut self) {
+        let handle = std::mem::replace(&mut self.handle, unsafe { std::mem::uninitialized() });
+        handle.clear();
+    }
+}