The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6c75fd3d1679f09efb95ea486cb26f3d13431b92

commit 6c75fd3d1679f09efb95ea486cb26f3d13431b92
Author: Marijn Kruisselbrink <mek@chromium.org>
Date: Tue Apr 24 18:20:06 2018

[FileAPI] Synchronously terminate loader when abort is called().

Otherwise loads started right after calling abort() won't work.

Also simplify the watching logic in MojoBlobReader, to prevent hitting
DCHECKs in OnResponseBodyStreamReady.

Bug:  835928 
Change-Id: I45eec517ccaf5f830101b6a02fce2fdcf696d17b
Reviewed-on: https://chromium-review.googlesource.com/1024315
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553204}
[modify] https://crrev.com/6c75fd3d1679f09efb95ea486cb26f3d13431b92/storage/browser/blob/mojo_blob_reader.cc
[modify] https://crrev.com/6c75fd3d1679f09efb95ea486cb26f3d13431b92/third_party/WebKit/LayoutTests/external/wpt/FileAPI/reading-data-section/FileReader-multiple-reads.html
[modify] https://crrev.com/6c75fd3d1679f09efb95ea486cb26f3d13431b92/third_party/blink/renderer/core/fileapi/file_reader.cc