1313140 - Avoid triggering `onChangeViewportDevice` for every resize

Status: RESOLVED FIXED

(DevTools :: Responsive Design Mode, defect, P3)

Description

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

At the moment, we call `onChangeViewportDevice` in resizable-viewport.js for every size change, which trickles down to RDP calls each time.

We really only need to do this a single time to transition away from an active device (if there is one).

Not yet sure if the most natural way in React is to either:

A. Fire an action every time, but the reducer for it only triggers `onChangeViewportDevice` on actual change
B. Filter to actual change directly at the event handler and only call `onChangeViewportDevice` on actual change there

Comment 1

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

Remove this step does appear to improve pref on resize, though it's a bit hard to tell for sure.  I do see less JS activity in the profile.

(Make sure to disable debug JS libs like react-dev when profiling!)

Comment 2

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

Patches in bug 1319950 should resolve this.

Comment 3

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

Seems like this was fixed in 52+.