Bugfix in resumable uploader.
Bugfix in resumable uploader.

The resumable uploader was missing the last chunk in certain cases.

R=sgjesse@google.com

Review URL: https://codereview.chromium.org//574593003

close2/discoveryapis_generator,close2/discoveryapis_generator,financeCoding/discovery_api_dart_client_generator,financeCoding/discovery_api_dart_client_generator