The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/860ec28b1e0fd5de1cff7d5e0e56bbb02ad07f0f

commit 860ec28b1e0fd5de1cff7d5e0e56bbb02ad07f0f
Author: Jennifer Apacible <apacible@chromium.org>
Date: Tue Aug 28 18:50:18 2018

[Picture in Picture] Hide controls when the window is resizing/dragged.

Currently, the controls on the Picture-in-Picture window are shown while
the window is being resized or dragged. The scaling of the controls is
not very smooth while the window is resized.

The controls cannot be interacted with during the resize and dragging
actions. They also slightly obscure the video, especially the play/pause
icon. Removing the controls will allow the user to view the final video
size and position.

The controls are shown again when the user hovers over / interacts with
the window.

Bug:  877987 
Change-Id: Ic50b2a330a811540914d9675b068cc561a652bbd
Reviewed-on: https://chromium-review.googlesource.com/1191026
Reviewed-by: CJ DiMeglio <lethalantidote@chromium.org>
Commit-Queue: apacible <apacible@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586800}
[modify] https://crrev.com/860ec28b1e0fd5de1cff7d5e0e56bbb02ad07f0f/chrome/browser/ui/views/overlay/overlay_window_views.cc
[modify] https://crrev.com/860ec28b1e0fd5de1cff7d5e0e56bbb02ad07f0f/chrome/browser/ui/views/overlay/overlay_window_views.h

Tested the issue on chrome reported version# 70.0.3534.4 using Ubuntu 14.04 with steps mentioned below:
1) Launched chrome reported version and enabled PIP flag from Chrome://flags
2) Opened the URL: https://japacible.github.io/sandbox/index.html and resized the video, didn't observed any janky in the controls

@Jennifer Apacible: Please find the attached screencast for your reference and let us know if we missed anything in reproducing the issue and help us in verifying the fix.

Thanks!

Deleted: 877987.ogv 2.6 MB

	877987.ogv 2.6 MB View Download

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bd8a51d5a8b6ff221ac49e18c1a224a9ef4810d0

commit bd8a51d5a8b6ff221ac49e18c1a224a9ef4810d0
Author: Jennifer Apacible <apacible@chromium.org>
Date: Thu Aug 30 23:16:38 2018

[Picture in Picture] Hide controls on all platforms while resizing/moving.

This change hides the controls on the Picture-in-Picture window on all
platforms while moving the window or when the size updates. Previously,
this was handled on Windows.

The controls cannot be interacted with during the resize and dragging
actions. They also slightly obscure the video, especially the play/pause
icon. Removing the controls will allow the user to view the final video
size and position.

Bug:  877987 
Change-Id: I788d8cb5690e3c587f93b21ad7eb7d0a2c69ecef
Reviewed-on: https://chromium-review.googlesource.com/1197722
Reviewed-by: CJ DiMeglio <lethalantidote@chromium.org>
Commit-Queue: apacible <apacible@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587832}
[modify] https://crrev.com/bd8a51d5a8b6ff221ac49e18c1a224a9ef4810d0/chrome/browser/ui/views/overlay/overlay_window_views.cc
[modify] https://crrev.com/bd8a51d5a8b6ff221ac49e18c1a224a9ef4810d0/chrome/browser/ui/views/overlay/overlay_window_views.h