The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3d5dfd57596024f8302fa2135f5f53b83b3d96bb

commit 3d5dfd57596024f8302fa2135f5f53b83b3d96bb
Author: Shimi Zhang <ctzsm@chromium.org>
Date: Fri Jul 28 03:45:32 2017

aw: Migrate one FILE task to TaskScheduler

This CL: 

Migrate a task on FILE thread to TaskScheduler
in android_webview/browser/aw_contents_io_thread_client.cc
by replacing FILE thread with a SequencedTaskRunner.

It also removes redundant aw_contents_background_thread_client.{h,cc}
since we can make JNI calls in browser layer now.

Bug:  749365 
Change-Id: I08a47ae93737c48a3ecfac917ac970bf2374472d
Reviewed-on: https://chromium-review.googlesource.com/588379
Reviewed-by: Selim Gurun <sgurun@chromium.org>
Commit-Queue: Shimi Zhang <ctzsm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490248}
[modify] https://crrev.com/3d5dfd57596024f8302fa2135f5f53b83b3d96bb/android_webview/BUILD.gn
[delete] https://crrev.com/cc1ba99f6a33d33bafc0e69ddb16d428af000635/android_webview/browser/aw_contents_background_thread_client.cc
[delete] https://crrev.com/cc1ba99f6a33d33bafc0e69ddb16d428af000635/android_webview/browser/aw_contents_background_thread_client.h
[modify] https://crrev.com/3d5dfd57596024f8302fa2135f5f53b83b3d96bb/android_webview/browser/aw_contents_io_thread_client.cc
[modify] https://crrev.com/3d5dfd57596024f8302fa2135f5f53b83b3d96bb/android_webview/browser/aw_contents_io_thread_client.h

gab@, the migration is done, but I still have two questions

1) We are using Callback, do we need to migrate to OnceCallback as well?
2) It seems it is safer to check base::ThreadRestrictions::AssertIOAllowed(); to replace DCHECK_CURRENTLY_ON(BrowserThread::FILE); in aw_contents_background_thread_client.cc, is that recommended?

Thanks!

Thanks!

1) Callback -> OnceCallback is always desirable where possible but isn't part of the TaskScheduler migration

2) Yes

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2b58140dd30194534c00bd7ce6e1aba191b6a2c4

commit 2b58140dd30194534c00bd7ce6e1aba191b6a2c4
Author: Shimi Zhang <ctzsm@chromium.org>
Date: Tue Aug 08 17:12:04 2017

aw: Add AssertIOAllowed()

As a part for migrate to TaskScheduler.

Function RunShouldInterceptRequest might be involved in IO calls, so
add AssertIOAllowed to ensure the behavior.

Bug:  749365 
Change-Id: I8e4b274d73e25f349f8250bbf9e89139995e7cb9
Reviewed-on: https://chromium-review.googlesource.com/604707
Reviewed-by: Bo Liu <boliu@chromium.org>
Commit-Queue: Shimi Zhang <ctzsm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#492673}
[modify] https://crrev.com/2b58140dd30194534c00bd7ce6e1aba191b6a2c4/android_webview/browser/aw_contents_io_thread_client.cc