Start incremental marking only if there are enough promoted objects since the last GC.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index d2986682782a71303c9d1060315ef2e57afb2150..a7caea9322004e14d5d598bd91360de1c9a7dec3 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -117,6 +117,7 @@ Heap::Heap()
       old_gen_allocation_limit_(kMinimumAllocationLimit),
       old_gen_limit_factor_(1),
       size_of_old_gen_at_last_old_space_gc_(0),
+      total_promoted_at_last_old_space_gc_(0),
       external_allocation_limit_(0),
       amount_of_external_allocated_memory_(0),
       amount_of_external_allocated_memory_at_last_global_gc_(0),
@@ -796,6 +797,7 @@ bool Heap::PerformGarbageCollection(GarbageCollector collector,
     UpdateSurvivalRateTrend(start_new_space_size);
 
     size_of_old_gen_at_last_old_space_gc_ = PromotedSpaceSize();
+    total_promoted_at_last_old_space_gc_ = PromotedTotalSizeOfObjects();
 
     if (high_survival_rate_during_scavenges &&
         IsStableOrIncreasingSurvivalTrend()) {