Various fixes to make github less error-prone

[Manishearth]

r? @Ms2ger

[highfive]

Warning

• These commits modify unsafe code. Please review it carefully!

[Manishearth]

I run this with the userscript:

window.history = {};
CanvasRenderingContext2D.prototype.fillText = function(a,b,c) {alert(a);alert(b);alert(c);}
document.domain="";
dqs = Document.prototype.querySelector;
Document.prototype.querySelector = function(a) {
    alert("doc.qS: "+a);
    if (a == ':target') {
        return null;
    }
    ret = dqs.apply(this, [a]);
    alert("doc.qS over");
    return ret;
}
delete window.WebSocket;

WebSocket is broken because we coerce [] in its constructor to "", which then causes a SyntaxError. querySelector is broken because we don't support :target, though I'm working on that.

window.history isn't easy to fix now since we don't really have the browsing context framework. I haven't yet looked at document.domain or filltext().

We also need support for form.elements

[bors-servo]

☔ The latest upstream changes (presumably #7710) made this pull request unmergeable. Please resolve the merge conflicts.

[Ms2ger]

Please squash into logical commits that pass tests for review.

[Manishearth]

Done

[nox]

Reviewed 1 of 2 files at r2, 8 of 8 files at r3.
Review status: 9 of 11 files reviewed at latest revision, 1 unresolved discussion, all commit checks successful.

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^{tests/wpt/metadata/html/semantics/forms/form-control-infrastructure/form.html.ini, line 3 [r3] (raw file):}
Please file a follow-up issue for those that remain.

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Comments from the review on Reviewable.io

[Ms2ger]

@bors-servo r+

Do file that issue.

[bors-servo]

📌 Commit 982e55a has been approved by Ms2ger

[bors-servo]

⌛ Testing commit 982e55a with merge 2623f58...

[bors-servo]

☀️ Test successful - android, gonk, linux-dev, linux-rel, mac-dev-ref-unit, mac-rel-css, mac-rel-wpt