Can you provide a screen shot?
Also I tried to follow these steps, but when a new window shows up, there isn't a video element. 

Here's screen recording where we can see the white splash at the beginning that doesn't happen with current media controls.

Deleted: white-splash.webm 2.3 MB

	white-splash.webm 2.3 MB View Download

Oops!

I forgot to mention that I had turned on the "New Media Controls" flag at chrome://flags/#enable-modern-media-controls

Were you not able to reproduce this when the flag was disabled?

Nope. I wasn't seeing any white splash without the flag.

I can also reproduce on twitter. Check out https://twitter.com/Google/status/935993288410087424 to see a white splash before video plays for instance.

This could be the default poster.

Does that mean they use <video controls> for some reasons? I assume the poster shouldn't show up unless the controls are there, right?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3a4fe158c1ef2b8ca5619510a530434cc5d90455

commit 3a4fe158c1ef2b8ca5619510a530434cc5d90455
Author: Tommy Steimel <steimel@chromium.org>
Date: Fri Jan 12 17:41:49 2018

Hide the loading panel when the media controls are hidden

This CL adds handler methods to the loading panel element so that the
MediaControlsImpl can inform the loading panel that the controls are
hidden, and therefore the loading panel should hide as well. This
solves a bug where the loading panel was displaying on videos that did
not use the native media controls.

Bug:  787448 
Change-Id: Ie0349b2090a4ad354974a28d8c6469349e1968e4
Reviewed-on: https://chromium-review.googlesource.com/839983
Commit-Queue: Tommy Steimel <steimel@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#528985}
[modify] https://crrev.com/3a4fe158c1ef2b8ca5619510a530434cc5d90455/third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.cpp
[modify] https://crrev.com/3a4fe158c1ef2b8ca5619510a530434cc5d90455/third_party/WebKit/Source/modules/media_controls/elements/MediaControlLoadingPanelElement.cpp
[modify] https://crrev.com/3a4fe158c1ef2b8ca5619510a530434cc5d90455/third_party/WebKit/Source/modules/media_controls/elements/MediaControlLoadingPanelElement.h
[modify] https://crrev.com/3a4fe158c1ef2b8ca5619510a530434cc5d90455/third_party/WebKit/Source/modules/media_controls/elements/MediaControlLoadingPanelElementTest.cpp

It is definitely fixed for https://hangouts.google.com/ in Chrome 65.0.3321.0 canary on Mac for but it still fails visually at https://twitter.com/Google/status/935993288410087424.

hmm that's strange since I was testing using that twitter link. Does it still fail on today's canary?

My bad, twitter video is fixed in Chrome 65.0.3323.0 canary on Mac.
Thank you!