base: improve the WaitContext doc test

Use the PollToken derive and the build_with() function to make the
example more representative of actual uses.

BUG=None
TEST=cargo doc
TEST=cargo test -p base --doc wait_context

Change-Id: I1f154dfd6247786024dc94035ea63db11968e85a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3630424
Reviewed-by: Dennis Kempin <denniskempin@google.com>
Reviewed-by: Noah Gold <nkgold@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>

base/src/wait_context.rs

@@ -44,24 +44,48 @@ pub enum EventType {
 /// # Example
 ///
 /// ```
-/// # use base::{
-///     Result, Event, WaitContext,
-/// };
-/// # fn test() -> Result<()> {
-///     let evt1 = Event::new()?;
-///     let evt2 = Event::new()?;
-///     evt2.write(1)?;
+/// use base::{Event, PollToken, Result, WaitContext};
 ///
-///     let ctx: WaitContext<u32> = WaitContext::new()?;
-///     ctx.add(&evt1, 1)?;
-///     ctx.add(&evt2, 2)?;
+/// #[derive(PollToken, Copy, Clone, Debug, PartialEq)]
+/// enum ExampleToken {
+///    SomeEvent(u32),
+///    AnotherEvent,
+/// }
 ///
-///     let events = ctx.wait()?;
-///     let tokens: Vec<u32> = events.iter().filter(|e| e.is_readable)
-///         .map(|e| e.token).collect();
-///     assert_eq!(tokens, [2]);
-/// #   Ok(())
-/// # }
+/// let evt1 = Event::new()?;
+/// let evt2 = Event::new()?;
+/// let another_evt = Event::new()?;
+///
+/// let ctx: WaitContext<ExampleToken> = WaitContext::build_with(&[
+///     (&evt1, ExampleToken::SomeEvent(1)),
+///     (&evt2, ExampleToken::SomeEvent(2)),
+///     (&another_evt, ExampleToken::AnotherEvent),
+/// ])?;
+///
+/// // Trigger one of the `SomeEvent` events.
+/// evt2.write(1)?;
+///
+/// // Wait for an event to fire. `wait()` will return immediately in this example because `evt2`
+/// // has already been triggered, but in normal use, `wait()` will block until at least one event
+/// // is signaled by another thread or process.
+/// let events = ctx.wait()?;
+/// let tokens: Vec<ExampleToken> = events.iter().filter(|e| e.is_readable)
+///     .map(|e| e.token).collect();
+/// assert_eq!(tokens, [ExampleToken::SomeEvent(2)]);
+///
+/// // Reset evt2 so it doesn't trigger again in the next `wait()` call.
+/// let _ = evt2.read()?;
+///
+/// // Trigger a different event.
+/// another_evt.write(1)?;
+///
+/// let events = ctx.wait()?;
+/// let tokens: Vec<ExampleToken> = events.iter().filter(|e| e.is_readable)
+///     .map(|e| e.token).collect();
+/// assert_eq!(tokens, [ExampleToken::AnotherEvent]);
+///
+/// let _ = another_evt.read()?;
+/// # Ok::<(), base::Error>(())
 /// ```
 pub struct WaitContext<T: EventToken>(EventContext<T>);
 

third_party/minijail

@@ -1 +1 @@
-Subproject commit ff062d54f9a419e149f726b69aea8cd509158927
+Subproject commit 4170a270c9db983ffdbbd6c464494fc4432319b3