Make Win64 compile.

src/spaces.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 334 matching lines @@
 
   int store_buffer_counter() { return store_buffer_counter_; }
   void set_store_buffer_counter(int counter) {
     store_buffer_counter_ = counter;
   }
 
   Address body() { return address() + kObjectStartOffset; }
 
   Address body_limit() { return address() + size(); }
 
-  int body_size() { return size() - kObjectStartOffset; }
+  int body_size() { return static_cast<int>(size() - kObjectStartOffset); }
 
   bool Contains(Address addr) {
     return addr >= body() && addr < address() + size();
   }
 
   // Checks whether addr can be a limit of addresses in this page.
   // It's a limit if it's in the page, or if it's just after the
   // last byte of the page.
   bool ContainsLimit(Address addr) {
     return addr >= body() && addr <= address() + size();
@@ skipping 2201 matching lines @@
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_H_