url: add sort() to URLSearchParams

[jasnell]

whatwg/url#26 proposes adding a sort() capability to URLSearchParams. The idea would be to have a simple default lexical sort of keys. If added, we would need to add this to the API

[targos]

PR: whatwg/url#199

Note: the current proposal requires a stable sorting algorithm.

[TimothyGu]

whatwg/url#199 has been merged.

Is there an existing stable sort function in the code base? If not, I'll just make a simple insertion sort (or copy the one in V8), which is stable.

[joyeecheung]

If we use an array of tuples as the underlying data structure instead of flattening them out, we can just use Array.prototype.sort. Any reason they must be flattened?

[joyeecheung]

Also I remember there was discussion about moving the parsing bit to C++, for reference, blink does it with a Vector<std::pair<String, String>> and gecko does it with a nsTArray<Param>(essentially a vector with pair of strings too)

[TimothyGu]

@joyeecheung, we can't use array.sort because it is not guaranteed to be stable, while the WHATWG spec does. In C++, creating new arrays for each tuple seems to be fairly expensive, so I decided on a flattened array instead.