Fix building on 64-bit Windows

test/cctest/test-debug.cc

 // Copyright 2007-2008 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 2193 matching lines @@
   char* pos1 = strstr(message, prefix);
   if (pos1 == NULL) {
     return false;
   }
   pos1 += strlen(prefix);
   char* pos2 = strchr(pos1, '"');
   if (pos2 == NULL) {
     return false;
   }
   Vector<char> buf(buffer, buffer_size);
-  int len = pos2 - pos1;
+  int len = static_cast<int>(pos2 - pos1);
   if (len > buffer_size - 1) {
     len = buffer_size - 1;
   }
   OS::StrNCpy(buf, pos1, len);
   buffer[buffer_size - 1] = '\0';
   return true;
 }
 
 
 struct EvaluateResult {
@@ skipping 3848 matching lines @@
 
   break_point_hit_count = 0;
   foo->Call(env->Global(), 0, NULL);
   CHECK_EQ(1, break_point_hit_count);
 
   v8::Debug::SetDebugEventListener(NULL);
   debugee_context = v8::Handle<v8::Context>();
   debugger_context = v8::Handle<v8::Context>();
   CheckDebuggerUnloaded();
 }