Thanks for filing the issue!

Checked the issue on reported chrome version 64.0.3282.167 and on the latest canary 66.0.3355.0 using Mac 10.13.1 with the below mentioned steps.
1. Launched Chrome 
2. Navigated to https://jsfiddle.net/bdq674ow/22/
Our Observations:
* On version 64.0.3282.167 for the first time we are to select only one letter later even after refreshing the jsfiddle page, we could not select one or more letters i.e., it's locked. Attaching the screen cast of the same for reference.
* On version 60.0.3072.0 similar behaviour is seen as that of the above mentioned version, and checked on the latest version too. Attaching the screen cast of the same for reference. 

@Reporter: We are not very clear about it's behaviour as we can only select the letter for the first time. Could you please confirm whether chrome version 60.0.3072.0 has an issue too, by looking at the attached screen cast "816714- M60 and M66.mp4"? 

Deleted: 816714 on Reported version.mp4 2.2 MB

	816714 on Reported version.mp4 2.2 MB View Download

Deleted: 816714- M60 and M66.mp4 5.1 MB

	816714- M60 and M66.mp4 5.1 MB View Download

I can confirm that 60 is showing the error also. The videos capture the issue very well:
- only allows 1 selection
- locks after first choice

Thank you for providing more feedback. Adding the requester to the cc list.

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

I reproduced this. This depends on "Show scroll bars" setting in System Preferences. It seems this issue happens only if the setting is set to "When scrolling".

As per the confirmation given by the reporter in comment#4, it is clearly understood that issue is there from M60. Hence, considering it as Non-Regression and removing Needs-Bisect label. 
Note: As this is a non-regression issue adding labels M-66, FoundIn-66 and Target-66, Please remove if not required.

Thanks!

Issue is not seen on Windows and Ubuntu 14.04, it is specific to Mac.

Thanks!

Chao can you investigate this?

It seems related to overlay scrollbar. On Aura with overlay scrollbar, it works but shows with a scrollbar.

Deleted: Screenshot from 2018-03-08 14-41-09.png 2.6 KB

	Screenshot from 2018-03-08 14-41-09.png 2.6 KB View Download

This issue is caused by:
1. we did not set the correct visibility state for overlay scrollbars.
2. if we set the size 5, but giving 8 option, select must have a scrollbar then the select will be annoying for overlay scrollbar. Maybe we should consider give <select> a  minimum width as Safari. Also the overlay scrollbar on select can not drag by mouse.

  

Deleted: Screen Shot 2018-03-09 at 19.46.52.png 8.0 KB

	Screen Shot 2018-03-09 at 19.46.52.png 8.0 KB View Download

We should fix #1 so that scrollbars only steal clicks while they're visible.

IMO, authors can adjust the width themselves if they find scrollbars overlay content so I'm not too concerned about that. We should fix the scrollbar not being able to be dragged though.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/177e20da67ed035c0c2300e73f2cefc7e0a5206d

commit 177e20da67ed035c0c2300e73f2cefc7e0a5206d
Author: chaopeng <chaopeng@chromium.org>
Date: Fri Mar 16 17:45:36 2018

Correct the scrollbars_hidden_if_overlay_ initial state

This issue is caused by we create vertical overlay scrollbar for <select> but
not call ShowOverlayScrollbar since it does not need it. But we set the
scrollbars hidden to false in ScrollableArea ctor which is not correct for
overlay scrollbars. Overlay scrollbars (include Android, Aura, Mac) are hidden
when creation.

In this patch, we set scrollbars_hidden_if_overlay_ true in ScrollableArea ctor.
It would not affect to non overlay scrollbars since we check for
UsesOverlayScrollbars() before read scrollbars_hidden_if_overlay_.

This patch also rename scrollbars_hidden_ to scrollbars_hidden_if_overlay_.

Bug:  816714 
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I5256fb99750cd3e7b7081231eada87572817bfe3
Reviewed-on: https://chromium-review.googlesource.com/957480
Commit-Queue: Jianpeng Chao <chaopeng@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: weiliangc <weiliangc@chromium.org>
Reviewed-by: Rick Byers <rbyers@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543756}
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/cc/layers/layer.cc
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/cc/layers/layer_client.h
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/cc/test/mock_layer_client.h
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/LayoutTests/plugins/overlay-scrollbar-mouse-capture.html
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/core/frame/LocalFrameView.cpp
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/core/layout/ScrollbarsTest.cpp
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/core/paint/PaintLayerScrollableAreaTest.cpp
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/core/testing/Internals.cpp
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/platform/exported/WebScrollbarThemeClientImpl.cpp
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/platform/exported/WebScrollbarThemeClientImpl.h
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/platform/scroll/ScrollableArea.h
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/platform/scroll/Scrollbar.cpp
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/platform/scroll/Scrollbar.h
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/platform/scroll/ScrollbarTestSuite.h
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/platform/scroll/ScrollbarThemeClient.h
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/platform/scroll/ScrollbarThemeMac.mm
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlayTest.cpp
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/ui/compositor/layer.cc
[modify] https://crrev.com/177e20da67ed035c0c2300e73f2cefc7e0a5206d/ui/compositor/layer.h

nice!