Optimize third-party request check

[mjethani]

Background

In #7232 the third-party request checking code was moved into adblockpluscore. This code is one of the hot spots, and now it can be optimized using some simple tricks:

• Use a Map object rather than a plain object
• Avoid Array.prototype.split and Array.prototype.join, instead use a while loop and String.prototype.indexOf
• Avoid String.prototype.replace with a regular expression unless required
• Split into smaller generic functions for later reuse

What to change

Make the above changes.

Hints for testers

Make sure that filters with $third-party and ~third-party (not third-party, i.e. first-party) flags are working as expected. For example, the filter foo$third-party should block a request to http://foo.com/foo from http://bar.com/ but not from http://foo.com/ itself. Similarly, the filter bar$~third-party should block a request to http://bar.com/bar from http://bar.com/ but not from http://foo.com/.

Note that the significant part of the change here is figuring out what "third-party" means. foo.example.com and bar.example.com are considered to be the same domain; therefore, a request from one to the other is not third-party. But foo.com and bar.com are not the same domain, therefore a request from one to the other is third-party. Please test for this.

[abpbot]

A commit referencing this issue has landed:
​Issue 7250 - Optimize third-party request check

[abpbot]

A commit referencing this issue has landed:
​Issue 7250 - Optimize third-party request check