1129093 - HistoryMenu __proto__ assignment triggers: "chrome://...browser.js, line 4763: mutating the [[Prototype]] of an object will cause your code to run very slowly; instead create the object with the correct initial [[Prototype]] value using Object.create"

Status: RESOLVED WONTFIX

(Firefox :: Bookmarks & History, defect)

Description

[Daniel Holbert [:dholbert]]

Noticed this go by in my debug build's terminalspew:
{
JavaScript warning: chrome://browser/content/browser.js, line 4763: mutating the [[Prototype]] of an object will cause your code to run very slowly; instead create the object with the correct initial [[Prototype]] value using Object.create
}

This points to the __proto__ assignment here:

> 496 // View for the history menu.
> 497 function HistoryMenu(aPopupShowingEvent) {
> 498   // Workaround for Bug 610187.  The sidebar does not include all the Places
> 499   // views definitions, and we don't need them there.
> 500   // Defining the prototype inheritance in the prototype itself would cause
> 501   // browser.js to halt on "PlacesMenu is not defined" error.
> 502   this.__proto__.__proto__ = PlacesMenu.prototype;

http://mxr.mozilla.org/mozilla-central/source/browser/base/content/browser-places.js?rev=a3d02e44a476#502

Setting dependency on bug 632411, which added this chunk, and bug 610187, which is mentioned in the code-comment.

Comment 2

[:Gijs (he/him)]

This warning was removed in bug 1049041 so I guess we should close this wontfix? I doubt that for places interactions, these proto rearrangements are going to be the bottleneck at this point. Either way, moving to the correct component...

Comment 3

[Marco Bonardo [:mak]]

Yeah, this is not critical, these views should be rewritten anyway, and in a new world they'd be classes in their own modules, not this proto mess.