Summary: Send part of the response body every 100 ms if the client has set onreadystatechange. This
is done by using the same events as the iOS code and removing the callback that Android previously
used.
Reconsolidate iOS and Android implementations.
Closes#3772
public
Reviewed By: mkonicek
Differential Revision: D2647005
fb-gh-sync-id: d006e566867fa47d5f8dff71219cb390bcb8e15a