Fix download PDF document with server extra data.

In case of range request, if server send unexpectedly
extra data, ignore it.

BUG=825829

Steps to reproduce:
1) Clear browser cache.
2) Open PDF:
http://www.major-landrover.ru/upload/attachments/f/9/f96aab07dab04ae89c8a509ec1ef2b31.pdf#page=55
3) Wait until document finish loading

Expected:
 The loading of document is finished
Actual:
 Some times the loading of document is never finished.

Change-Id: I46fc8001bea5701e1e93d26d1ea6527d4736ff05
Reviewed-on: https://chromium-review.googlesource.com/1094634
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Art Snake <art-snake@yandex-team.ru>
Cr-Commit-Position: refs/heads/master@{#567257}
3 files changed