Display the AutoFill preview string in the drop down box.

Native code now provides us with a preview string as well as
an autofill query id. Display the preview string in the
drop down box.

Requires a change in external/webkit:
https://android-git.corp.google.com/g/#change,77132

Change-Id: Ia5e26b98546cda1090142f1720f6a7836be6595c