Fix Win64 build.

src/spaces.h

 // Copyright 2006-2008 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 573 matching lines @@
 
   // Returns the maximum available bytes of heaps.
   static intptr_t Available() {
     return capacity_ < size_ ? 0 : capacity_ - size_;
   }
 
   // Returns allocated spaces in bytes.
   static intptr_t Size() { return size_; }
 
   // Returns the maximum available executable bytes of heaps.
-  static int AvailableExecutable() {
+  static intptr_t AvailableExecutable() {
     if (capacity_executable_ < size_executable_) return 0;
     return capacity_executable_ - size_executable_;
   }
 
   // Returns allocated executable spaces in bytes.
   static intptr_t SizeExecutable() { return size_executable_; }
 
   // Returns maximum available bytes that the old space can have.
   static intptr_t MaxAvailable() {
     return (Available() / Page::kPageSize) * Page::kObjectAreaSize;
@@ skipping 1664 matching lines @@
 
  private:
   LargeObjectChunk* current_;
   HeapObjectCallback size_func_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_H_