+1. 

this appears to have stopped happening, was it a script issue on monorail?

okay, this is really flaky, it's started happening again, and it's not just monorail it's also other websites e.g. uma dashboards. I don't know what's triggering it.

wfh@ Thanks for the issue.

Able to reproduce the issue on Windows 10, Mac OS 10.12.6 and Ubuntu 14.04 on the latest Canary 66.0.3343.3 and Dev 65.0.3325.51 by following the below steps.

1. Launched Chrome and navigated to a bug which has a long scroll. (eg. https://bugs.chromium.org/p/chromium/issues/detail?id=810413&desc=2).
2. Enabled the Flag 'Scroll Anchor Serialization' in chrome://flags and relaunch chrome.
3. Scrolled to the bottom of the bug, right-clicked on any link and can observe that the scroll bar jumps to the top of the page.

Note: - This issue is not observed when the Flag 'Scroll Anchor Serialization' is disabled.
      - This issue is seen only on first reload of the page and when the scroll bar is at the top of the page.

pnoland@ Can you please check and confirm if this issue is related to the recently pushed experiment on Dev and Canary.

wfh@ Can you please retry the issue by disabling the flag "Scroll Anchor Serialization" in chrome://flags and update the thread with the observations.

Thanks..

Yup this is directly related to that flag. I've already started on the fix.

 Issue 810366  has been merged into this issue.

I never enabled the flag, is it enabled by a field trial? If so, can you disable the field trial (0%)? This is extremely annoying (Chrome 65 dev).

#4 - at first, it was happening just once, but on Google Search, middle clicking any link post-scroll scrolls up and preventDefaults the middle click. Right clicking does not exhibit the issue (fortunately, so I can open in a new tab).

There was a field trial enabled but it was disabled on Friday the 9th. It's possible you haven't restarted your browser since then. 

I restart my browser daily (unfortunately).
(As it turns out, I am using Chrome 66 dev on Windows 7)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4d4df345da7dd17a7143063d0e0f22b4a3a8f652

commit 4d4df345da7dd17a7143063d0e0f22b4a3a8f652
Author: Patrick Noland <pnoland@chromium.org>
Date: Mon Feb 26 19:25:56 2018

Fix several scroll anchor serialization bugs

1) Fix crashes caused by premature/forbidden usage of javascript.
Given that we don't need or want to produce a real exception, this is
accomplished using DummyExceptionStateForTesting.
2) Add checks for layoutBox() truthiness.
3) Save the relative offset in FindAnchor so that it updates properly.
4) Make the implementation work nicely with root layer scrolling by
adding RestoreAnchor to ScrollableArea, implementing it on
PaintLayerScrollableArea, and calling restore on the view's
LayoutViewportScrollableArea.

Bug: 810161, 810897 , 810474 
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I820e572cef543ed85156622fd574684109488eec
Reviewed-on: https://chromium-review.googlesource.com/922384
Commit-Queue: Patrick Noland <pnoland@google.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Steve Kobes <skobes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539230}
[modify] https://crrev.com/4d4df345da7dd17a7143063d0e0f22b4a3a8f652/content/browser/session_history_browsertest.cc
[modify] https://crrev.com/4d4df345da7dd17a7143063d0e0f22b4a3a8f652/content/browser/site_per_process_browsertest.cc
[add] https://crrev.com/4d4df345da7dd17a7143063d0e0f22b4a3a8f652/content/test/data/page_with_samesite_iframe.html
[modify] https://crrev.com/4d4df345da7dd17a7143063d0e0f22b4a3a8f652/third_party/WebKit/Source/core/frame/LocalFrameView.cpp
[modify] https://crrev.com/4d4df345da7dd17a7143063d0e0f22b4a3a8f652/third_party/WebKit/Source/core/frame/LocalFrameView.h
[modify] https://crrev.com/4d4df345da7dd17a7143063d0e0f22b4a3a8f652/third_party/WebKit/Source/core/layout/ScrollAnchor.cpp
[modify] https://crrev.com/4d4df345da7dd17a7143063d0e0f22b4a3a8f652/third_party/WebKit/Source/core/layout/ScrollAnchor.h
[modify] https://crrev.com/4d4df345da7dd17a7143063d0e0f22b4a3a8f652/third_party/WebKit/Source/core/layout/ScrollAnchorTest.cpp
[modify] https://crrev.com/4d4df345da7dd17a7143063d0e0f22b4a3a8f652/third_party/WebKit/Source/core/loader/FrameLoader.cpp
[modify] https://crrev.com/4d4df345da7dd17a7143063d0e0f22b4a3a8f652/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
[modify] https://crrev.com/4d4df345da7dd17a7143063d0e0f22b4a3a8f652/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.h
[modify] https://crrev.com/4d4df345da7dd17a7143063d0e0f22b4a3a8f652/third_party/WebKit/Source/platform/scroll/ScrollableArea.h