The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f77194e375c11f0c0d95a71502d47f9e45b17213

commit f77194e375c11f0c0d95a71502d47f9e45b17213
Author: Justin Cohen <justincohen@google.com>
Date: Wed Jun 20 14:43:26 2018

[ios] Disable ios_web_inttests::ForwardPostNavigation on iOS12

TBR=eugenebut@chromium.org

Bug:  854615 
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I7cc280c03203696c0fa00081b15736d6245d4ba5
Reviewed-on: https://chromium-review.googlesource.com/1107880
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568837}
[modify] https://crrev.com/f77194e375c11f0c0d95a71502d47f9e45b17213/ios/web/web_state/navigation_and_load_callbacks_inttest.mm

NavigationAndLoadCallbacksTest.ForwardPostNavigation passes locally. Justin, where you able to repro this failure locally? 

Yes, I am.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9d6b357513480e5eb472902cd69fac3f2c1747c4

commit 9d6b357513480e5eb472902cd69fac3f2c1747c4
Author: Eugene But <eugenebut@chromium.org>
Date: Mon Jun 25 15:40:38 2018

Fix NavigationAndLoadCallbacksTest.ForwardPostNavigation for iOS 12.

WebStatePolicyDecider::ShouldAllowResponse is now called when going back
after the form submission. Updated test expectation to match new
behavior.

Bug:  854615 
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: Icd3357750f56e9f4cac5a158fdd8aeb54dbf6c4b
Reviewed-on: https://chromium-review.googlesource.com/1113449
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570048}
[modify] https://crrev.com/9d6b357513480e5eb472902cd69fac3f2c1747c4/ios/web/web_state/navigation_and_load_callbacks_inttest.mm