gn: Fix stale references in Parser::AssignComments().

tools/gn/parser.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/parser.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 833 matching lines @@
   // Assign suffix to syntax immediately before.
   cur_comment = static_cast<int>(suffix_comment_tokens_.size() - 1);
   for (std::vector<const ParseNode*>::const_reverse_iterator i = post.rbegin();
        i != post.rend();
        ++i) {
     // Don't assign suffix comments to the function, list, or block, but instead
     // to the last thing inside.
     if ((*i)->AsFunctionCall() || (*i)->AsList() || (*i)->AsBlock())
       continue;
 
-    const Location& start = (*i)->GetRange().begin();
-    const Location& end = (*i)->GetRange().end();
+    Location start = (*i)->GetRange().begin();
+    Location end = (*i)->GetRange().end();
 
     // Don't assign suffix comments to something that starts on an earlier
     // line, so that in:
     //
     // sources = [ "a",
     //     "b" ] # comment
     //
     // it's attached to "b", not sources = [ ... ].
     if (start.line_number() != end.line_number())
       continue;
 
     while (cur_comment >= 0) {
       if (end.byte() <= suffix_comment_tokens_[cur_comment].location().byte()) {
         const_cast<ParseNode*>(*i)->comments_mutable()->append_suffix(
             suffix_comment_tokens_[cur_comment]);
         --cur_comment;
       } else {
         break;
       }
     }
 
     // Suffix comments were assigned in reverse, so if there were multiple on
     // the same node, they need to be reversed.
     if ((*i)->comments() && !(*i)->comments()->suffix().empty())
       const_cast<ParseNode*>(*i)->comments_mutable()->ReverseSuffix();
   }
 }