The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9364e47b961b5889d2d960553d09311437e5907f

commit 9364e47b961b5889d2d960553d09311437e5907f
Author: Nate Fischer <ntfschr@chromium.org>
Date: Thu Aug 10 20:28:51 2017

AW: ensure initSafeBrowsing callback is invoked on UI thread

This wraps initSafeBrowsing()'s callback in another callback. The
wrapperCallback is responsible for running the actual callback on the
UI thread. This is to stay consistent about which thread the
callback is actually invoked on.

Bug:  754061 
Test: run_webview_instrumentation_test_apk -f SafeBrowsingTest#testInitSafeBrowsingCallbackOnUIThread
Change-Id: I49a37443ba283884679dac7f521da007e5aec117
Reviewed-on: https://chromium-review.googlesource.com/609412
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Tobias Sargeant <tobiasjs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#493516}
[modify] https://crrev.com/9364e47b961b5889d2d960553d09311437e5907f/android_webview/java/src/org/chromium/android_webview/AwContentsStatics.java
[modify] https://crrev.com/9364e47b961b5889d2d960553d09311437e5907f/android_webview/javatests/src/org/chromium/android_webview/test/SafeBrowsingTest.java

I'm on the fence about whether or not this is merge-worthy. I'm requesting the merge, but amineer@ should take a look at my reasoning below (and feel free to disagree with it).

Q: How will this help our users?
A: This guarantees that the callback is invoked on a consistent thread. This impacts app stability/bugs. Without this guarantee, applications may incorrectly assume the UI thread is always used, causing bugs for the edge cases when we use a different thread.

Q: Is this necessary?
A: Not critical, but we shouldn't make thread guarantees without merging this back, and I think the API will be lacking without those guarantees. tobiasjs@ let me know if you agree/disagree.

This should be on the safer-side for merges:

 * Only affects android_webview/
 * I anticipate a clean merge
 * Full automated test coverage

This bug requires manual review: M61 has already been promoted to the beta branch, so this requires manual review
Please contact the milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), ketakid@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

We can take this for 61 so long as we merge ahead of next beta.  Thus, approved for M61 branch 3163, but please merge by EOD.  Thanks!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c7f4188a67c7e0dea2610fada3efa714302d2bf5

commit c7f4188a67c7e0dea2610fada3efa714302d2bf5
Author: Nate Fischer <ntfschr@chromium.org>
Date: Mon Aug 14 18:35:34 2017

AW: ensure initSafeBrowsing callback is invoked on UI thread

This wraps initSafeBrowsing()'s callback in another callback. The
wrapperCallback is responsible for running the actual callback on the
UI thread. This is to stay consistent about which thread the
callback is actually invoked on.

TBR=ntfschr@chromium.org

(cherry picked from commit 9364e47b961b5889d2d960553d09311437e5907f)

Bug:  754061 
Test: run_webview_instrumentation_test_apk -f SafeBrowsingTest#testInitSafeBrowsingCallbackOnUIThread
Change-Id: I49a37443ba283884679dac7f521da007e5aec117
Reviewed-on: https://chromium-review.googlesource.com/609412
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Tobias Sargeant <tobiasjs@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#493516}
Reviewed-on: https://chromium-review.googlesource.com/614129
Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/branch-heads/3163@{#541}
Cr-Branched-From: ff259bab28b35d242e10186cd63af7ed404fae0d-refs/heads/master@{#488528}
[modify] https://crrev.com/c7f4188a67c7e0dea2610fada3efa714302d2bf5/android_webview/java/src/org/chromium/android_webview/AwContentsStatics.java
[modify] https://crrev.com/c7f4188a67c7e0dea2610fada3efa714302d2bf5/android_webview/javatests/src/org/chromium/android_webview/test/SafeBrowsingTest.java

Thanks, Alex!

Bulk edit: marking stale 'fixed' bugs as 'verified' since they don't need verification at this point.