This PR updates http2/core to need less bindings and closures when emitting various events, instead it uses the already existing ability of process.nextTick and setImmediate to pass through arguments. Despite having to use a rest parameter, this is actually faster than binding or creating a closure. My understanding is that with V8 6.2 this code will only get faster.

(Also there's a minor fix for the fact that incorrect headers passed to the various respond with file methods weren't correctly exiting after an error and instead continued to run the rest of the function.)

I adjusted the existing headers benchmark to use a few more of the affected functions and the benchmark result is below (this is over 250 iterations for each node version). Not a huge difference but probably still worthwhile. (The headers benchmark is the best for assessing these changes because it runs into these event emits on both the client and the server. I only used nheaders at 0 because the other variations stress the wrong parts of the system that we don't care about.)

http2/headers.js nheaders=0 n=1000       1.80 %        *** 6.068982e-12

I've also added tests to cover most of these emits throughout the code. There are a few spots left uncovered but I'll need to figure out a slightly different way of testing than just mocking the handle method to output error codes. I don't think that should hold up this PR though as they were already not covered by tests.

Thanks for reviewing!

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

http2, test