Fix webkit_unit_tests.isolate to use ' instead of ".

Source/web/webkit_unit_tests.isolate

 # Copyright (c) 2015 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': {
     'files': [
       '<(PRODUCT_DIR)/content_shell.pak',
       'tests/data/',
       # Required by some image decoder tests.
       '../platform/image-decoders/testing/',
@@ skipping 18 matching lines @@
           '<(DEPTH)/testing/test_env.py',
           '<(PRODUCT_DIR)/webkit_unit_tests<(EXECUTABLE_SUFFIX)',
         ],
       },
     }],
   ],
   'includes': [
     '../../../../base/base.isolate',
     '../../../../gin/v8.isolate',
     # Required on Android to copy icudtl.dat to a device.
-    "../../../../third_party/icu/icu.isolate",
+    '../../../icu/icu.isolate',
   ],
 }