1438640 - Tracking Protection Stats js: remove mutation observer if possible

Status: RESOLVED INVALID

(Firefox for iOS :: General, enhancement)

Description

[:garvan]

Currently we use Focus iOS js for tracking protection stats, but we are interested in make some improvements based on this review:
https://github.com/mozilla-mobile/firefox-ios/pull/3631#discussion_r168561189

"""
@justindarc
A couple things here:

    I'd like to see if we can just hijack HTMLScriptElement.prototype.src like we do for Image above?
    Does hijacking Image.prototype.src above actually work for appending <img>s to the DOM in all cases? i.e.: var img = document.createElement('img'); img.src = '/foo.jpg'; document.body.appendChild(img);
    If we do actually have to use a MutationObserver for <script> elements, we need to at least check for the existence of src before calling postMessage(). For instance, I think it's possible to append a <script> to the DOM that has inline JS.

You can test those cases with this JSBin: http://output.jsbin.com/rahizoq
"""

Comment 1

[:garvan]

See also https://bugzilla.mozilla.org/show_bug.cgi?id=1438639
Bug for automated test which will help when refactoring the JS

Comment 2

[:garvan]

Another comment from the review is to use one mutation observer for both scripts and images.

Comment 3

[Justin D'Arcangelo [:justindarc]]

Closing since we must rely on MO to do this.