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

mojo/edk/system/mock_simple_dispatcher.cc

Index: mojo/edk/system/mock_simple_dispatcher.cc
diff --git a/mojo/edk/system/mock_simple_dispatcher.cc b/mojo/edk/system/mock_simple_dispatcher.cc
index 2e429e46d32718eb7d07f50a2b9a0f3903cc8976..eb44ec071de28b5a732f8441108600185ab6c927 100644
--- a/mojo/edk/system/mock_simple_dispatcher.cc
+++ b/mojo/edk/system/mock_simple_dispatcher.cc
@@ -27,8 +27,9 @@ void MockSimpleDispatcher::SetSatisfiedSignals(
   if (new_satisfied_signals == state_.satisfied_signals)
     return;
 
+  HandleSignalsState old_state = state_;
   state_.satisfied_signals = new_satisfied_signals;
-  HandleSignalsStateChangedNoLock();
+  OnHandleSignalsStateChangeNoLock(old_state, state_);
 }
 
 void MockSimpleDispatcher::SetSatisfiableSignals(
@@ -42,8 +43,9 @@ void MockSimpleDispatcher::SetSatisfiableSignals(
   if (new_satisfiable_signals == state_.satisfiable_signals)
     return;
 
+  HandleSignalsState old_state = state_;
   state_.satisfiable_signals = new_satisfiable_signals;
-  HandleSignalsStateChangedNoLock();
+  OnHandleSignalsStateChangeNoLock(old_state, state_);
 }
 
 Dispatcher::Type MockSimpleDispatcher::GetType() const {