Fix Win64 compilation problem.

BUG=

Review URL: https://codereview.chromium.org/12379043

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13785 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/spaces.h

@@ -1745,7 +1745,7 @@ class PagedSpace : public Space {
     first_unswept_page_ = first;
   }
 
-  void IncrementUnsweptFreeBytes(int by) {
+  void IncrementUnsweptFreeBytes(intptr_t by) {
     unswept_free_bytes_ += by;
   }
 
@@ -1754,7 +1754,7 @@ class PagedSpace : public Space {
     unswept_free_bytes_ += (p->area_size() - p->LiveBytes());
   }
 
-  void DecrementUnsweptFreeBytes(int by) {
+  void DecrementUnsweptFreeBytes(intptr_t by) {
     unswept_free_bytes_ -= by;
   }