1364398 - Firefox doesn't restore windows into a rounded size when it comes with 2 or more windows if 'privacy.resistFingerprinting' is true

Status: RESOLVED WORKSFORME

(Core :: XUL, defect, P2)

Description

[afnankhan]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:55.0) Gecko/20100101 Firefox/55.0
Build ID: 20170511063838

Steps to reproduce:

Firefox doesn't remember window maximized state both on startup or when I open new window when privacy.resistFingerprinting is true. I am using latest Nightly.
1. Set privacy.resistFingerprinting to true
2. Maximize window if not maximized
3. Open new window
4. Close Firefox in maximized state
5. Open Firefox again


Actual results:

1. New window doesn't open maximized
2. Firefox doesn't open in maximized state


Expected results:

1. New window should open maximized if current window is maximized
2. Firefox should open in maximized state if it was close maximized

I am using Windows 10 and Firefox Nightly

Comment 1

[Loic]

Did it use to work with previous nightlies and same settings?

Comment 2

[Loic]

Regression range:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=4c7c05a49f3ce40aa0969beccb397380a8907f4a&tochange=fc2eda92be4091d5ea0828f51fe4aaee41ed8319

It's a side effect of bug 1330882. And IMHO, it's probably by design to reduce fingerprinting by monitoring the size of the display window. 

Tim, could you confirm this behaviour is expected?

Comment 3

[Tim Huang[:timhuang]]

The session restore will intentionally not to restore window size when 'privacy.resistfingerprinting' is true. The purpose of this behavior is to mitigate browser fingerprinting. So, yes, this behavior is expected.

Comment 4

[Loic]

Ty.

Comment 6

[Nazar Mokrynskyi]

1. If user changed window size, new dimensions should be preserved, user can always open a new window with default size of 1000x1000
2. If there are 2 windows on browser restart only first one is resized to 1000x1000

So this issue is not fixed in either way.

Comment 7

[Loic]

Tim, how is managed the case with 2 (or more) windows open? Should Firefox resize all windows with the size of 1000x1000?

Comment 8

[Tim Huang[:timhuang]]

Yes, Firefox should resize all windows into 1000x1000 for preventing browser fingerprinting. I will looking into it.

Comment 9

[Tim Huang[:timhuang]]

It appears to me that the problem which was mentioned by comment 6 is no longer shown for the latest nightly, Build ID: 20180115220459. I have run a bisect and it turns out that this problem was fixed after Bug 1365541 was landed. So, I think we can close this bug.