Remove 'read_only': 1 from most .isolate files.

components/nacl_helper_nonsfi_unittests.isolate

 # 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.
 {
   'conditions': [
     ['OS=="linux"', {
       'variables': {
         'command': [
           '<(PRODUCT_DIR)/nacl_helper_nonsfi_unittests',
         ],
         'files': [
           '<(PRODUCT_DIR)/nacl_helper_nonsfi_unittests',
           '<(PRODUCT_DIR)/nacl_helper_nonsfi_unittests_main',
         ],
-        'read_only': 1,
       },
     }],
   ],
 }