[fuchsia_async] Add impl WakeupTime for fuchsia_zircon::Duration

Fixed: 87477

Change-Id: I98af0dffe8ae9f709ec048bd38ba36b612607653
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/613642
Commit-Queue: Ilya Yanok <yanok@google.com>
Reviewed-by: Adam Perry <adamperry@google.com>

src/lib/fuchsia-async/src/runtime/mod.rs

diff --git a/src/lib/fuchsia-async/src/runtime/mod.rs b/src/lib/fuchsia-async/src/runtime/mod.rs
index 5d9a7d3..51aed3f 100644
--- a/src/lib/fuchsia-async/src/runtime/mod.rs
+++ b/src/lib/fuchsia-async/src/runtime/mod.rs
@@ -61,6 +61,13 @@
     }
 }
 
+#[cfg(target_os = "fuchsia")]
+impl WakeupTime for Duration {
+    fn into_time(self) -> Time {
+        Time::after(self)
+    }
+}
+
 impl DurationExt for std::time::Duration {
     fn after_now(self) -> Time {
         self.into_time()
@@ -300,6 +307,17 @@
         }
     }
 
+    #[cfg(target = "fuchsia")]
+    #[test]
+    fn can_use_zx_duration() {
+        let mut exec = LocalExecutor::new().unwrap();
+        let start = Instant::now();
+        let timer = Timer::new(Duration::from_millis(100));
+        exec.run_singlethreaded(timer);
+        let end = Instant::now();
+        assert!(end - start > std::time::Duration::from_millis(100));
+    }
+
     #[test]
     fn can_detect_stalls() {
         use std::sync::atomic::{AtomicU64, Ordering};