Avoid excessive GCs in small heaps.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 62c3821ed7cf55af13546032cf2ba46db862c722..b51eb0c33be315d057199adb16d89ecfc3f59442 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -5298,7 +5298,7 @@ intptr_t Heap::CalculateOldGenerationAllocationLimit(double factor,
   CHECK(factor > 1.0);
   CHECK(old_gen_size > 0);
   intptr_t limit = static_cast<intptr_t>(old_gen_size * factor);
-  limit = Max(limit, kMinimumOldGenerationAllocationLimit);
+  limit = Max(limit, old_gen_size + kMinimumOldGenerationAllocationLimit);
   limit += new_space_.Capacity();
   intptr_t halfway_to_the_max = (old_gen_size + max_old_generation_size_) / 2;
   return Min(limit, halfway_to_the_max);