base: Erase unused FOR_EACH_OBSERVER macro.

PRESUBMIT.py

 # Copyright (c) 2012 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.
 
 """Top-level presubmit script for Chromium.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into depot_tools.
 """
 
@@ skipping 290 matching lines @@
     ),
     (
       '#pragma comment(lib,',
       (
         'Specify libraries to link with in build files and not in the source.',
       ),
       True,
       (),
     ),
     (
-      r'FOR_EACH_OBSERVER(',
-      (
-        'Use range-based for loops to iterate through base::ObserverList, e.g.',
-        '        for (auto& observer : observers) { observer.Observe(); }',
-      ),
-      True,
-      (),
-    ),
-    (
       r'STLDeleteContainerPointers',  # http://crbug.com/555865
       (
         'This call is obsolete with C++ 11; create a container with owning',
         'pointers instead (e.g. std::vector<std::unique_ptr<x>> ).',
       ),
       True,
       (),
     ),
     (
       r'STLDeleteElements',  # http://crbug.com/555865
@@ skipping 1970 matching lines @@
   results.extend(input_api.canned_checks.CheckTreeIsOpen(
       input_api,
       output_api,
       json_url='http://chromium-status.appspot.com/current?format=json'))
 
   results.extend(input_api.canned_checks.CheckChangeHasBugField(
       input_api, output_api))
   results.extend(input_api.canned_checks.CheckChangeHasDescription(
       input_api, output_api))
   return results