cros_async: allow wakers to be canceled

Allowing for wakers to be canceled will allow futures that register
wakers properly implement `Drop`. As it is, they won't ever fire but the
saved FD will leak.

TEST=added 'cancel' unit test to fd_executor:
"cargo test cancel" from the cros_async directory.
Change-Id: Iab5bea6aac0cc689392997745f5dcc8c285200d9

Change-Id: I1df1a04897e8d2c5e9c414d84998084607209fb9
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2164074
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
Commit-Queue: Dylan Reid <dgreid@chromium.org>
Tested-by: Dylan Reid <dgreid@chromium.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/async_core/src/eventfd.rs b/async_core/src/eventfd.rs
index b930f07..fdff83e 100644
--- a/async_core/src/eventfd.rs
+++ b/async_core/src/eventfd.rs
@@ -109,7 +109,7 @@ impl Stream for EventFd {
             .or_else(|e| {
                 if e.errno() == EWOULDBLOCK {
                     add_read_waker(self.inner.as_raw_fd(), cx.waker().clone())
-                        .map(|()| Poll::Pending)
+                        .map(|_token| Poll::Pending)
                         .map_err(Error::AddingWaker)
                 } else {
                     Err(Error::EventFdRead(e))