[heap] Old generation limit is based on capacity.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 74b9d85a15aed7ce8ec43fd23986cfa8cd01b7c8..ecb08fb0a77cdec86a7568000d1a586570853532 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -625,11 +625,9 @@ class Heap {
     return old_space_->allocation_limit_address();
   }
 
-  // TODO(hpayer): There is still a missmatch between capacity and actual
-  // committed memory size.
-  bool CanExpandOldGeneration(int size = 0) {
+  bool CanExpandOldGeneration(int size) {
     if (force_oom_) return false;
-    return (CommittedOldGenerationMemory() + size) < MaxOldGenerationSize();
+    return (OldGenerationCapacity() + size) < MaxOldGenerationSize();
   }
 
   // Clear the Instanceof cache (used when a prototype changes).
@@ -1192,6 +1190,9 @@ class Heap {
   // more spaces are needed until it reaches the limit.
   intptr_t Capacity();
 
+  // Returns the capacity of the old generation.
+  intptr_t OldGenerationCapacity();
+
   // Returns the amount of memory currently committed for the heap.
   intptr_t CommittedMemory();