Add different behavior to AwakableList for "persistent" vs "one-shot" awakables.

mojo/edk/system/async_waiter.cc

Index: mojo/edk/system/async_waiter.cc
diff --git a/mojo/edk/system/async_waiter.cc b/mojo/edk/system/async_waiter.cc
index 15122a367c05f003befdc1dbc1fe6c90f7177bc4..130fcc09693d0fad252878b88f369cace0bcc084 100644
--- a/mojo/edk/system/async_waiter.cc
+++ b/mojo/edk/system/async_waiter.cc
@@ -11,12 +11,11 @@ AsyncWaiter::AsyncWaiter(const AwakeCallback& callback) : callback_(callback) {}
 
 AsyncWaiter::~AsyncWaiter() {}
 
-bool AsyncWaiter::Awake(uint64_t /*context*/,
+void AsyncWaiter::Awake(uint64_t /*context*/,
                         AwakeReason reason,
                         const HandleSignalsState& /*signals_state*/) {
   callback_(MojoResultForAwakeReason(reason));
   delete this;
-  return false;
 }
 
 }  // namespace system