Sync defines with the GYP build.

build/common.gypi

 # 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 2916 matching lines @@
       ['enable_session_service==1', {
         'defines': ['ENABLE_SESSION_SERVICE=1'],
       }],
       ['enable_themes==1', {
         'defines': ['ENABLE_THEMES=1'],
       }],
       ['enable_autofill_dialog==1', {
         'defines': ['ENABLE_AUTOFILL_DIALOG=1'],
       }],
       ['enable_prod_wallet_service==1', {
+        # In GN, this is set on the autofill tagets only. See
+        # //components/autofill/core/browser:wallet_service
         'defines': ['ENABLE_PROD_WALLET_SERVICE=1'],
       }],
       ['enable_background==1', {
         'defines': ['ENABLE_BACKGROUND=1'],
       }],
       ['enable_google_now==1', {
         'defines': ['ENABLE_GOOGLE_NOW=1'],
       }],
       ['cld_version!=0', {
         'defines': ['CLD_VERSION=<(cld_version)'],
@@ skipping 3237 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }