gn: attach comments to parse tree

tools/gn/header_checker.cc

 // Copyright 2014 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/header_checker.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/files/file_util.h"
@@ skipping 42 matching lines @@
 LocationRange CreatePersistentRange(const InputFile& input_file,
                                     const LocationRange& range) {
   InputFile* clone_input_file;
   std::vector<Token>* tokens;  // Don't care about this.
   scoped_ptr<ParseNode>* parse_root;  // Don't care about this.
 
   g_scheduler->input_file_manager()->AddDynamicInput(
       input_file.name(), &clone_input_file, &tokens, &parse_root);
   clone_input_file->SetContents(input_file.contents());
 
-  return LocationRange(
-      Location(clone_input_file, range.begin().line_number(),
-               range.begin().char_offset()),
-      Location(clone_input_file, range.end().line_number(),
-               range.end().char_offset()));
+  return LocationRange(Location(clone_input_file,
+                                range.begin().line_number(),
+                                range.begin().char_offset(),
+                                -1 /* TODO(scottmg) */),
+                       Location(clone_input_file,
+                                range.end().line_number(),
+                                range.end().char_offset(),
+                                -1 /* TODO(scottmg) */));
 }
 
 // Given a reverse dependency chain where the target chain[0]'s includes are
 // being used by chain[end] and not all deps are public, returns the string
 // describing the error.
 std::string GetDependencyChainPublicError(
     const HeaderChecker::Chain& chain) {
   std::string ret = "The target:\n  " +
       chain[chain.size() - 1].target->label().GetUserVisibleName(false) +
       "\nis including a file from the target:\n  " +
@@ skipping 438 matching lines @@
       for (size_t i = 0; i < private_deps.size(); i++) {
         if (breadcrumbs.insert(
                 std::make_pair(private_deps[i].ptr, cur_link)).second)
           work_queue.push(ChainLink(private_deps[i].ptr, false));
       }
     }
   }
 
   return false;
 }