1278548 - Current private window design causes all content to twitch when I toggle tracking protection

Status: UNCONFIRMED

(Firefox :: Private Browsing, defect, P3)

Description

[arni2033]

Attachment: screencast 1 - private window twitch russian.webm

> My Info:   Win7_64, Nightly 49 ru, 32bit, ID 20160526082509, screen 1366x768, DPI = 100%
STR:
 1.A) Open private window (Ctrl+Shift+P)  in russian localization of Nightly (ru)
 1.B) Open private window (Ctrl+Shift+P), execute in console:
      titleTracking.innerHTML="Приватный просмотр с Защитой от отслеживания"
 2. Disable tracking protection
 3. Hover mouse over the toggle ("#tpButton"), then click

AR:  All page content is abruptly moved to the bottom by ~48px
ER:  No content movement, just like in en-US version


Notes:
 1) My opinion is that if UI suggests content twitching that moves click target from under the mouse
    pointer, then UI is bad. At the same time UI that causes twitching below click target is still OK
    (e.g. about:preferences#privacy -> change "Nightly will" to "use custom settings for history")
 2) I use words "twitch" and "twitching" for all occurrences of unexpected content movement
    If there's a more suitable word for that, please correct the summary
 3) It's possible to preserve extra space to prevent any twitching. See CSS hack below:

#titleTracking.hide{
    display: inline !important;
    visibility: hidden !important;
}
.title{
    background-position: left top !important;
    position: relative !important;
}
#title{
    position: absolute !important;
}