Fix Win64 compilation problems introduced by r9932.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index 6fe4928f23dc06cb26ff2305f0e86998f6700c7e..0cbe13f92fb26cdb730318ae56cde11cac517d23 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -1011,12 +1011,13 @@ void PromotionQueue::RelocateQueueHead() {
   intptr_t* head_end =
       Min(front_, reinterpret_cast<intptr_t*>(p->body_limit()));
 
-  int entries_count = (head_end - head_start) / kEntrySizeInWords;
+  int entries_count =
+      static_cast<int>(head_end - head_start) / kEntrySizeInWords;
 
   emergency_stack_ = new List<Entry>(2 * entries_count);
 
   while (head_start != head_end) {
-    int size = *(head_start++);
+    int size = static_cast<int>(*(head_start++));
     HeapObject* obj = reinterpret_cast<HeapObject*>(*(head_start++));
     emergency_stack_->Add(Entry(obj, size));
   }