title: Contains references to both AndroidX and old support library
body: <p>After upgrating flutter version to <strong>Flutter 1.22.0-2.0.pre.78 • channel master</strong> I am getting this warning:-</p>
  <blockquote>
  <p>WARNING:
  [Processor] Library
  'C:\Users....gradle\caches\modules-2\files-2.1\io.flutter\flutter_embedding_debug\1.0.0-b1d9f863db32cb1d6714cf75db4a992ee3765113\b8748b5192a2a0961f5c14f8845331ad5f2225a1\flutter_embedding_debug-1.0.0-b1d9f863db32cb1d6714cf75db4a992ee3765113.jar'
  contains references to both AndroidX and old support library. This
  seems like the library is partially migrated. Jetifier will try to
  rewrite the library anyway.  Example of androidX reference:
  'androidx/annotation/VisibleForTesting'  Example of support library
  reference: 'android/support/annotation/NonNull'`</p>
  </blockquote>
  <p>Is this issue will cause some serious issue in future or not. Thanks in Advance :)</p>