UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36

Steps to reproduce the problem:
1. Open https://jsfiddle.net/4jxc1qty/6/ in Chrome on Windows 10 with a display that has devicePixelRatio > 1.

2. Observe that as you move the mouse across the example page, the accumulated movementX increases faster than the accumulated (screenX - prevScreenX) values. The difference should be negligible, but in the test they're off by a factor of window.devicePixelRatio.

What is the expected behavior?
In the W3C spec, `movementX` is `screenX - previousScreenX`

What went wrong?
movementX/Y values are scaled by window.devicePixelRatio and are 2x the values you get doing manual screenX - prevScreenX calculation.

Did this work before? N/A 

Does this work in other browsers? Yes

Chrome version: 70.0.3538.102  Channel: stable
OS Version: 10
Flash Version: 

I'm using Windows 10 and have an external display. I've tried devicePixelRatio 1.5 and also 2.0 (changed via Windows Display settings) and it's incorrect in both.

I've tested on macOS, in Firefox for Windows and in Edge, and all of them report movementX correctly.

I understand eirage's <eirage@chromium.org> patch in https://bugs.chromium.org/p/chromium/issues/detail?id=132914&q=movementX&colspec=ID%20Pri%20M%20Stars%20ReleaseBlock%20Component%20Status%20Owner%20Summary%20OS%20Modified has been reverted, but I think that it may be required to fix this.