Fix GN args merge issue for https://codereview.chromium.org/265693003

tools/gn/command_args.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 <stdio.h>
 #include <stdlib.h>
 
 #include <map>
 
 #include "base/command_line.h"
@@ skipping 180 matching lines @@
     OutputString("Waiting for editor on \"" + FilePathToUTF8(file_to_edit) +
                  "\"...\n");
     ::WaitForSingleObject(info.hProcess, INFINITE);
     ::CloseHandle(info.hProcess);
   }
   return true;
 }
 
 #else  // POSIX
 
-void RunEditor(const base::FilePath& file_to_edit) {
+bool RunEditor(const base::FilePath& file_to_edit) {
   // Prefer $VISUAL, then $EDITOR, then vi.
   const char* editor_ptr = getenv("VISUAL");
   if (!editor_ptr)
     editor_ptr = getenv("EDITOR");
   if (!editor_ptr)
     editor_ptr = "vi";
 
   std::string cmd(editor_ptr);
   cmd.append(" \"");
 
@@ skipping 126 matching lines @@
         "Or see \"gn help args\" for more variants.").PrintToStdout();
     return 1;
   }
 
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(kSwitchList))
     return ListArgs(args[0]);
   return EditArgsFile(args[0]);
 }
 
 }  // namespace commands