Introduce DONE state in idle notification handler.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 6b66818baef11911abc38f86b19ad2ab9de3acfc..e6770e5b4310471e9fb2b8ec2af367a7805aae54 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -4318,6 +4318,9 @@ bool Heap::IdleNotification(int idle_time_in_ms) {
 
   bool result = false;
   switch (action.type) {
+    case DONE:
+      result = true;
+      break;
     case DO_INCREMENTAL_MARKING:
       if (incremental_marking()->IsStopped()) {
         incremental_marking()->Start();
@@ -4340,7 +4343,6 @@ bool Heap::IdleNotification(int idle_time_in_ms) {
       mark_compact_collector()->EnsureSweepingCompleted();
       break;
     case DO_NOTHING:
-      result = true;
       break;
   }
   if (FLAG_trace_idle_notification) {