gyp: Move shim_headers.gypi from chromium.

icu.gyp

 # 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.
 
 {
   'includes': [
     'icu.gypi',
   ],
   'variables': {
     'use_system_icu%': 0,
@@ skipping 550 matching lines @@
               'unicode/uregex.h',
               'unicode/uregion.h',
               'unicode/usearch.h',
               'unicode/uspoof.h',
               'unicode/utmscale.h',
               'unicode/utrans.h',
               'unicode/vtzone.h',
             ],
           },
           'includes': [
-            '../../build/shim_headers.gypi',
+            'shim_headers.gypi',
           ],
           'toolsets': ['target'],
         },
         {
           'target_name': 'icuuc',
           'type': 'none',
           'dependencies': ['system_icu'],
           'export_dependent_settings': ['system_icu'],
           'variables': {
             'headers_root_path': 'source/common',
@@ skipping 82 matching lines @@
               'unicode/utf8.h',
               'unicode/utf.h',
               'unicode/utf_old.h',
               'unicode/utrace.h',
               'unicode/utypes.h',
               'unicode/uvernum.h',
               'unicode/uversion.h',
             ],
           },
           'includes': [
-            '../../build/shim_headers.gypi',
+            'shim_headers.gypi',
           ],
           'toolsets': ['target'],
         },
       ], # targets
     }],
   ], # conditions
 }