Crash on unexpected URL change.

TBR=eugenebut@google.com

(cherry picked from commit ba1815a412382038e41adc189134fcb1b75784aa)

Bug: 841105
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I4471a98cdef13e54b790ebcd565d59c67dba8bfd
Reviewed-on: https://chromium-review.googlesource.com/1054196
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Reviewed-by: Danyao Wang <danyao@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#558760}
Reviewed-on: https://chromium-review.googlesource.com/1060377
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/branch-heads/3396@{#609}
Cr-Branched-From: 9ef2aa869bc7bc0c089e255d698cca6e47d6b038-refs/heads/master@{#550428}
3 files changed