Chrome Version: Google Chrome	63.0.3239.132 (Official Build) (64-bit)
Revision	2e6edcfee630baa3775f37cb11796b1603a64360-refs/branch-heads/3239@{#709}
OS: Linux

What steps will reproduce the problem?
(1) Open any page in which the vertical scrollbar appears.
(2) Drag the "core" of the scrollbar up and down and keep holding the left mouse button.
(3) Right click. A context menu should appear.
(4) Let go of left mouse button.
(5) Left click outside the context menu and outside the scrollbar. The context menu should close.
(6) Note the bar is still darkened like it's being dragged. Hover the mouse pointer over various points of the scrollbar.

Expected: Hovering over the scrollbar has no effect.
Actual: The mouse is still dragging the scrollbar, even after letting go of the left mouse button, so the scrollbar and the page move.