Start incremental marking on idle notification.

src/incremental-marking.h

Index: src/incremental-marking.h
diff --git a/src/incremental-marking.h b/src/incremental-marking.h
index 30dbbc1605c7c5415767101469cc1f55c2d504ef..94500978b0b00882127a2734befc5ce79fadd19c 100644
--- a/src/incremental-marking.h
+++ b/src/incremental-marking.h
@@ -63,6 +63,8 @@ class IncrementalMarking {
 
   inline bool IsMarkingIncomplete() { return state() == MARKING; }
 
+  inline bool IsComplete() { return state() == COMPLETE; }
+
   bool WorthActivating();
 
   void Start();
@@ -97,6 +99,9 @@ class IncrementalMarking {
   // This is how much we increase the marking/allocating factor by.
   static const intptr_t kAllocationMarkingFactorSpeedup = 2;
   static const intptr_t kMaxAllocationMarkingFactor = 1000000000;
+  // This is given to Step() function when it is called without any allocation.
+  static const intptr_t kStepFakeAllocatedBytes = kAllocatedThreshold * 3;
+
 
   void OldSpaceStep(intptr_t allocated) {
     Step(allocated * kFastMarking / kInitialAllocationMarkingFactor);