Introduce DONE state in idle notification handler.

src/heap/gc-idle-time-handler.cc

Index: src/heap/gc-idle-time-handler.cc
diff --git a/src/heap/gc-idle-time-handler.cc b/src/heap/gc-idle-time-handler.cc
index cd7efe06523347dd70eff4848568648e266d3287..bc182ae5e40076513222193586cb2ed9ab6ab65d 100644
--- a/src/heap/gc-idle-time-handler.cc
+++ b/src/heap/gc-idle-time-handler.cc
@@ -18,6 +18,9 @@ const int GCIdleTimeHandler::kIdleScavengeThreshold = 5;
 
 void GCIdleTimeAction::Print() {
   switch (type) {
+    case DONE:
+      PrintF("done");
+      break;
     case DO_NOTHING:
       PrintF("no action");
       break;
@@ -74,7 +77,7 @@ GCIdleTimeAction GCIdleTimeHandler::Compute(size_t idle_time_in_ms,
     if (EnoughGarbageSinceLastIdleRound() || heap_state.contexts_disposed > 0) {
       StartIdleRound();
     } else {
-      return GCIdleTimeAction::Nothing();
+      return GCIdleTimeAction::Done();
     }
   }
   if (heap_state.incremental_marking_stopped) {