Reland r50057. This is exactly the same except with two lines cherrypicked from

chrome/chrome.gyp

 # Copyright (c) 2010 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.
 {
   'variables': {
     'chromium_code': 1,
 
     'variables': {
       'version_py_path': 'tools/build/version.py',
       'version_path': 'VERSION',
@@ skipping 430 matching lines @@
                 'branded_env': 'CHROMIUM_BUILD=chromium',
               }],
             ],
           },
           'inputs': [
             '<@(chrome_extra_resources_inputs)',
           ],
           'outputs': [
             '<(grit_out_dir)/grit/<(RULE_INPUT_ROOT).h',
             '<(grit_out_dir)/<(RULE_INPUT_ROOT).pak',
+            '<(grit_out_dir)/grit/<(RULE_INPUT_ROOT)_map.cc',
+            '<(grit_out_dir)/grit/<(RULE_INPUT_ROOT)_map.h',
             # TODO(bradnelson): move to something like this instead
             #'<!@(<(grit_info_cmd) --outputs \'<(grit_out_dir)\' <(chrome_resources_grds))',
             # This currently cannot work because gyp only evaluates the
             # outputs once (rather than per case where the rule applies).
             # This means you end up with all the outputs from all the grd
             # files, which angers scons and confuses vstudio.
             # One alternative would be to turn this into several actions,
             # but that would be rather verbose.
           ],
           'action': ['<@(grit_cmd)', '-i',
@@ skipping 1395 matching lines @@
       }],  # targets
     }],  # OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="solaris"
   ],  # 'conditions'
 }
 
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