Bug 1412346 part 5: (automated patch) Switch a bunch of C++ files in layout to use our standard mode lines. r=jfkthame

This patch was generated automatically by the "modeline.py" script, available
here: https://github.com/amccreight/moz-source-tools/blob/master/modeline.py

For every file that is modified in this patch, the changes are as follows:
 (1) The patch changes the file to use the exact C++ mode lines from the
     Mozilla coding style guide, available here:
https://developer.mozilla.org/en-US/docs/Mozilla/Developer_guide/Coding_Style#Mode_Line

 (2) The patch deletes any blank lines between the mode line & the MPL
     boilerplate comment.

 (3) If the file previously had the mode lines and MPL boilerplate in a
     single contiguous C++ comment, then the patch splits them into
     separate C++ comments, to match the boilerplate in the coding style.

MozReview-Commit-ID: EuRsDue63tK

Author: dholbert

layout/base/ArenaObjectID.h

@@ -1,4 +1,5 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

layout/base/ArenaRefPtr.h

@@ -1,6 +1,6 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
- * vim: set ts=2 sw=2 et tw=78:
- * This Source Code Form is subject to the terms of the Mozilla Public
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  */