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

mojo/edk/system/waiter.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/edk/system/waiter.h"
 
 #include "base/logging.h"
 #include "mojo/edk/platform/time_ticks.h"
 
 using mojo::platform::GetTimeTicks;
@@ skipping 74 matching lines @@
     }
   }
 
   if (context)
     *context = awake_context_;
   if (signals_state)
     *signals_state = signals_state_;
   return MojoResultForAwakeReason(awake_reason_);
 }
 
-bool Waiter::Awake(uint64_t context,
+void Waiter::Awake(uint64_t context,
                    AwakeReason reason,
                    const HandleSignalsState& signals_state) {
   MutexLocker locker(&mutex_);
 
   if (awoken_)
-    return true;
+    return;
 
   awoken_ = true;
   awake_reason_ = reason;
   signals_state_ = signals_state;
   awake_context_ = context;
   cv_.Signal();
   // |cv_.Wait()|/|cv_.WaitWithTimeout()| will return after |mutex_| is
   // released.
-  return true;
 }
 
 }  // namespace system
 }  // namespace mojo