Don't set the limit that triggers the next GC higher than the max

old space size.
Review URL: http://codereview.chromium.org/8491009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9892 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.h

@@ -1254,7 +1254,8 @@ class Heap {
         Max(old_gen_size + old_gen_size / divisor, kMinimumPromotionLimit);
     limit += new_space_.Capacity();
     limit *= old_gen_limit_factor_;
-    return limit;
+    intptr_t halfway_to_the_max = (old_gen_size + max_old_generation_size_) / 2;
+    return Min(limit, halfway_to_the_max);
   }
 
   intptr_t OldGenAllocationLimit(intptr_t old_gen_size) {
@@ -1263,7 +1264,8 @@ class Heap {
         Max(old_gen_size + old_gen_size / divisor, kMinimumAllocationLimit);
     limit += new_space_.Capacity();
     limit *= old_gen_limit_factor_;
-    return limit;
+    intptr_t halfway_to_the_max = (old_gen_size + max_old_generation_size_) / 2;
+    return Min(limit, halfway_to_the_max);
   }
 
   // Can be called when the embedding application is idle.