Start incremental marking on idle notification.

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index 4a1e01dcaa3135aa4ebd452259c847f60a9e70ab..e042957f31f76c2029db3c80cca73abebbdaa653 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -1757,6 +1757,12 @@ class Heap {
 
   void SelectScavengingVisitorsTable();
 
+  // Returns true if incremental marking is finished.
+  bool IdleIncrementalMarking();
+
+  // Returns true if no more GC work is left.
+  bool IdleGlobalGC();
+
   static const int kInitialSymbolTableSize = 2048;
   static const int kInitialEvalCacheSize = 64;
 
@@ -1782,6 +1788,13 @@ class Heap {
 
   IncrementalMarking incremental_marking_;
 
+  enum IdleWork {
+    IDLE_INCREMENTAL_MARKING,
+    IDLE_GLOBAL_GC
+  };
+
+  IdleWork idle_work_;
+
   int number_idle_notifications_;
   unsigned int last_idle_notification_gc_count_;
   bool last_idle_notification_gc_count_init_;