Chrome Version: 65.0.3325.89 (Official Build) beta (64-bit)
Chrome OS Version: 10323.39.0 (Official Build) beta-channel eve
Chrome OS Platform: Google Pixelbook
Network info: Switching between Wi-fi (built in), Ethernet (via USB-C dock)

Please specify Cr-* of the system to which this bug/feature applies (add
the label below).

Steps To Reproduce:
(1) Open browser windows that are large enough to include scrollbars
(2) Observe scrolling works with mousepad or touchscreen.
(3) Plug into external dock (specifically tested with Plugable USB-C Triple Display Dock)

Expected Result: Windows opened before plugging into the dock scroll properly with external mosue.

Actual Result: Windows opened before plugging into the dock do not respond to scrolling with external mouse.

How frequently does this problem reproduce? Always

What is the impact to the user, and is there a workaround? Close the window and re-open it.

Please provide any additional information below. Attach a screen shot or
log if possible.

For graphics-related bugs, please copy/paste the contents of the about:gpu
page at the end of this report.