Fix ResponseBodyLoader::DelegatingBytesConsumer

 - EndRead was missing when peeking bytes. Fix it and add a DCHECK
   in ReplayingBytesConsumer.
 - When DelegatingBytesConsumer uses up |lookahead_bytes_| in
   OnStateChange, keep reading instead of posting a task.

Bug: 894819
Change-Id: Iaafe6557ffa058aa1b0932de8073ff664fafdf37
Reviewed-on: https://chromium-review.googlesource.com/c/1460205
Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631162}
3 files changed