STR: 1. Have enough tabs that the left/right chevron scroll buttons are displayed. 2. Click and hold on one of the buttons. Actual results: The tab strip scrolls in steps, one tab at a time. Expected results: The tab strip scroll continuously. 10:36.94 INFO: Last good revision: db88d543de14b78333b095485de56cb8e9832af9 10:36.94 INFO: First bad revision: e1c23455946bd42445a0a12d223c7548c39c9785 10:36.94 INFO: Pushlog: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=db88d543de14b78333b095485de56cb8e9832af9&tochange=e1c23455946bd42445a0a12d223c7548c39c9785 It's probably bug 1356705.
More information from https://bugzilla.mozilla.org/show_bug.cgi?id=1387763 (resolved dup of this) 57.0a1 (2017-08-06) (32-bit) continues the jerky slow behaviour with < or > tab-bar scrolling Using mouse-wheel to scroll tabs remains acceptable smooth scroll. [ Keyboard arrows have no effect when tab is selected. I'm unsure of design spec. ] + Sometimes if I hold the "<", the tabs will move, but when I release the "<", they jump a further few places Playing around, I did note that using < or > can cause quite erratic jumps, worse under conditions of load = many browser windows & many tabs (+ maybe youtubes as well). Running under win10, on an oldish laptop dell Latitude D520 (adequate, 4GB, Core2 CPU T5600 @ 1.83GHz Works ok if I am cautious & caeful). I suspect less of a problem for more capable rigs. + I think there was a config item at one time to smooth-scroll tab-bar (which still happens if I use mousewheel); I wonder if that is/was relevant. + Noted also, possibly irrelevant clue: horizontal scrolling inside a large rendered webpage seems to have similar behaviour, moves in jumps.