The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d028982479f6173a0a20c274cd8bac2852fefaf6

commit d028982479f6173a0a20c274cd8bac2852fefaf6
Author: horo <horo@chromium.org>
Date: Tue Mar 01 09:46:20 2016

Reset fetch_dispatcher_ in ServiceWorkerVersionBrowserTest on IO thread.

The crashes ( issue 590400 ) happened while resetting |fetch_dispatcher_| in ServiceWorkerVersionBrowserTest::FetchOnRegisteredWorker().
https://chromium.googlesource.com/chromium/src/+/3fbfbe6e7690dd2b169cfaaae2ad7ac89537d74b/content/browser/service_worker/service_worker_browsertest.cc#458

|fetch_dispatcher_| is created on IO thread.
So it must be cleared on IO thread.

BUG= 590676 ,  590400 

Review URL: https://codereview.chromium.org/1750513002

Cr-Commit-Position: refs/heads/master@{#378421}

[modify] https://crrev.com/d028982479f6173a0a20c274cd8bac2852fefaf6/content/browser/service_worker/service_worker_browsertest.cc

The following revision refers to this bug:
  https://chrome-internal.googlesource.com/bling/chromium.git/+/d028982479f6173a0a20c274cd8bac2852fefaf6

commit d028982479f6173a0a20c274cd8bac2852fefaf6
Author: horo <horo@chromium.org>
Date: Tue Mar 01 09:46:20 2016