Fix DebugEvaluateWithoutStack test on Windows

Review URL: http://codereview.chromium.org/543115

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3653 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/cctest/test-debug.cc

@@ -2202,9 +2202,8 @@ bool GetEvaluateStringResult(char *message, char* buffer, int buffer_size) {
   if (pos == NULL) {
     return false;
   }
-  Vector<char> buf(buffer, buffer_size);
+  Vector<char> buf(buffer, buffer_size - 1);
   OS::StrNCpy(buf, pos, buffer_size);
-  buffer[buffer_size - 1] = '\0';
   return true;
 }