android_webview: stop using system expat.

android_webview/tools/known_issues.py

 # 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.
 
 """List of directories which are known issues for Android WebView.
 
 There are a number of directories in the Chromium tree which should be removed
 when merging into Android. Some are for licensing reasons; others are to ensure
 that the build inside the Android tree does not accidentally include the wrong
 headers.
@@ skipping 35 matching lines @@
         'third_party/sudden_motion_sensor',
         'third_party/swiftshader',
         'third_party/talloc',
         'third_party/webdriver',
         'third_party/wtl',
         'tools/telemetry/third_party/websocket-client',
 
         # Code we don't want to build/include by accident from the main chromium
         # src/ directory.
         'third_party/ashmem/*.[ch]',
-        'third_party/expat/files/lib',
         'third_party/libjpeg/*.[ch]',
     ],
     'third_party/icu': [
         # Incompatible code from ICU's repository.
         'source/data/brkitr',
     ],
 }
 
 KNOWN_INCOMPATIBLE['.'].extend(KNOWN_ISSUES)