Implement Drop for Proxy on macOS platform (#1526)

CHANGELOG.md

@@ -7,6 +7,7 @@
 - On X11, fix `ResumeTimeReached` being fired too early.
 - On Web, replaced zero timeout for `ControlFlow::Poll` with `requestAnimationFrame`
 - On Web, fix a possible panic during event handling
+- On macOS, fix `EventLoopProxy` leaking memory for every instance.
 
 # 0.22.0 (2020-03-09)
 

src/platform_impl/macos/event_loop.rs

@@ -117,6 +117,14 @@ pub struct Proxy<T> {
 
 unsafe impl<T: Send> Send for Proxy<T> {}
 
+impl<T> Drop for Proxy<T> {
+    fn drop(&mut self) {
+        unsafe {
+            CFRelease(self.source as _);
+        }
+    }
+}
+
 impl<T> Clone for Proxy<T> {
     fn clone(&self) -> Self {
         Proxy::new(self.sender.clone())