Remove 64-bit unclean line from heap size estimation

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index c4c806817e4e4eb03b614a0daf6e5b17fa695dfb..8a80c8c596478757be2c8b1ea0fbdd90a035dfd2 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -1081,7 +1081,6 @@ class Heap {
 
   inline intptr_t PromotedTotalSize() {
     int64_t total = PromotedSpaceSizeOfObjects() + PromotedExternalMemorySize();
-    if (total > kMaxInt) return static_cast<intptr_t>(kMaxInt);

[Hannes Payer (out of office), 2015/05/15 15:08:19]

Unfortunatly, an overflow is possible here. jkummerow, what caused the
regression?

     if (total < 0) return 0;
     return static_cast<intptr_t>(total);
   }