Sometimes, the mouse pointer will change to resizer cursor, and I can resize the PiP window by mouse pointer.
But, sometime, it does not. The cursor would not change.

Almost impossible.

Steps To Reproduce:

1. Enable Picture in Picture media.videocontrols.picture-in-picture.enabled=true if not
2. Play and Video
3. Enter Picture in Picture mode
4. Try to resize the Pip window by mouse

Actual Results:
The mouse pointer would not be changed to resizer cursor on the PiP window border.
Sometimes, the mouse pointer is changed to resizer cursor. But the pointer will be immediately changed to normal cursor.
So, I cannot resize the window.

Expected Results:
At least, A mouse pointer should react like main window.

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=32552726554321d35a8c18224343fe73ece324c2&tochange=0930049c0ca984c909d11ba2853ef6d96e43e242

Regressed by: 0930049c0ca984c909d11ba2853ef6d96e43e242 Mike Conley — Bug 1534389 - Send normal mouse events when cursor is over a draggable region on Windows. r=jmathies

:mconley,
Your patch seems to cause the regression. Can you please look into this?

Yes, I've added it to my queue - thank you for filing.

This is made easier by making the window-dragging region inset by 5px on each side.

Depends on D30100

https://hg.mozilla.org/mozilla-central/rev/93e59a14b907

I have the same problem with resizing the whole browser window.
Is this related and fixed as well?

Filed Bug 1549972

Removing the "qe-verify+ tag, considering the newly added bugs.

Also, Considering that the fix did not fix the reporter's issue, should it not be backed out?
This also applies to the clone of this bug: bug 1549972.

Build ID 20190626093633
User Agent Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:69.0) Gecko/20100101 Firefox/69.0

Verified as fixed on the latest Nightly build on Windows 10.

The original fix was backed out of beta 68, and I'm currently investigating the issue in bug 1557710.