Issue 6437 - Skip DOM-only patterns on initial load

This will be especially useful after https://codereview.adblockplus.org/29714601/

Ads are almost never part of the original HTML, they're loaded dynamically via JS or by some other means. In that case, particularly for the top-level frame, there's no need to traverse the DOM for DOM-only patterns until there's a mutation. This way when a mutation occurs we can target the newly added nodes quickly instead of waiting for a full traversal. If we do this, ads will be hidden immediately instead of appearing momentarily before disappearing as they do now.

[Manish Jethani, 2018-03-22 16:17:45]

Patch Set 1

See description.

[Manish Jethani, 2018-03-22 16:31:29]

Patch Set 2: Check if it's the top frame
Patch Set 3: Fix unrelated typo in comments

[hub, 2018-03-23 14:58:59]

https://codereview.adblockplus.org/29730630/diff/29730635/lib/content/elemHid...
File lib/content/elemHideEmulation.js (right):

https://codereview.adblockplus.org/29730630/diff/29730635/lib/content/elemHid...
lib/content/elemHideEmulation.js:463: if (typeof top != "undefined" &&
document.defaultView == top)
Maybe I'm missing something, but where does that `top` come from?

[Manish Jethani, 2018-03-23 16:56:46]

https://codereview.adblockplus.org/29730630/diff/29730635/lib/content/elemHid...
File lib/content/elemHideEmulation.js (right):

https://codereview.adblockplus.org/29730630/diff/29730635/lib/content/elemHid...
lib/content/elemHideEmulation.js:463: if (typeof top != "undefined" &&
document.defaultView == top)
On 2018/03/23 14:58:59, hub wrote:
> Maybe I'm missing something, but where does that `top` come from?

That's a reference to the global variable window.top, perhaps I should just
access it via the window object.

[hub, 2018-03-24 01:02:14]

https://codereview.adblockplus.org/29730630/diff/29730635/lib/content/elemHid...
File lib/content/elemHideEmulation.js (right):

https://codereview.adblockplus.org/29730630/diff/29730635/lib/content/elemHid...
lib/content/elemHideEmulation.js:463: if (typeof top != "undefined" &&
document.defaultView == top)
On 2018/03/23 16:56:46, Manish Jethani wrote:
> On 2018/03/23 14:58:59, hub wrote:
> > Maybe I'm missing something, but where does that `top` come from?
> 
> That's a reference to the global variable window.top, perhaps I should just
> access it via the window object.

I think it would be better, yes, both for clarity and safety.

[Manish Jethani, 2018-03-31 14:25:46]

I'm dropping this for now. I can't find a good way to do this without further
complicating the code. Ideally we would skip the DOM-only patterns when the
document's "readyState" is "loading" and then do the DOM-only patterns only (but
not any other patterns!) when the state changes to "complete". I'll see if I can
come back to do this, but I'm closing this for now.