Give AwakableList's wake-up method the old state in addition to the new state.

mojo/edk/system/awakable_list.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/awakable_list.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "mojo/edk/system/awakable.h"
 #include "mojo/edk/system/handle_signals_state.h"
 
 namespace mojo {
 namespace system {
 
 AwakableList::AwakableList() {
 }
 
 AwakableList::~AwakableList() {
   DCHECK(awakables_.empty());
 }
 
-void AwakableList::AwakeForStateChange(const HandleSignalsState& state) {
+void AwakableList::OnStateChange(const HandleSignalsState& old_state,
+                                 const HandleSignalsState& new_state) {
   // Instead of deleting elements in-place, swap them with the last element and
   // erase the elements from the end.
   auto last = awakables_.end();
   for (AwakeInfoList::iterator it = awakables_.begin(); it != last;) {
     bool keep = true;
-    if (state.satisfies(it->signals))
+    if (new_state.satisfies(it->signals) && !old_state.satisfies(it->signals))
       keep = it->awakable->Awake(MOJO_RESULT_OK, it->context);
-    else if (!state.can_satisfy(it->signals))
+    else if (!new_state.can_satisfy(it->signals) &&
+             old_state.can_satisfy(it->signals))
       keep = it->awakable->Awake(MOJO_RESULT_FAILED_PRECONDITION, it->context);
 
     if (!keep) {
       --last;
       std::swap(*it, *last);
     } else {
       ++it;
     }
   }
   awakables_.erase(last, awakables_.end());
@@ skipping 38 matching lines @@
       std::swap(*it, *last);
     } else {
       ++it;
     }
   }
   awakables_.erase(last, awakables_.end());
 }
 
 }  // namespace system
 }  // namespace mojo