Turn UploadDataStream into an abstract class, and split the implentation
into two classes - one for chunked uploads, one for non-chunked uploads.
This refactoring is aimed at allowing Cronet to add another
implementation for use on Android.
Splitting the logic for the chunked and non-chunked uploads isn't
necessary for that, but the two paths didn't share much code, and
keeping them as one class seems ugly.
BUG=412942
Review URL: https://codereview.chromium.org/560893004
Cr-Commit-Position: refs/heads/master@{#298966}
39 files changed
