Fix warnings on Win64.

src/debug.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 84 matching lines @@
   void SetOneShot();
   void ClearOneShot();
   void PrepareStepIn();
   bool IsExit() const;
   bool HasBreakPoint();
   bool IsDebugBreak();
   Object* BreakPointObjects();
   void ClearAllDebugBreak();
 
 
-  inline int code_position() { return pc() - debug_info_->code()->entry(); }
+  inline int code_position() {
+    return static_cast<int>(pc() - debug_info_->code()->entry());
+  }
   inline int break_point() { return break_point_; }
   inline int position() { return position_; }
   inline int statement_position() { return statement_position_; }
   inline Address pc() { return reloc_iterator_->rinfo()->pc(); }
   inline Code* code() { return debug_info_->code(); }
   inline RelocInfo* rinfo() { return reloc_iterator_->rinfo(); }
   inline RelocInfo::Mode rmode() const {
     return reloc_iterator_->rinfo()->rmode();
   }
   inline RelocInfo* original_rinfo() {
@@ skipping 746 matching lines @@
   Debug::AddressId id_;
   int reg_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 #endif  // V8_DEBUG_H_