Remove unnecessary PromiseEmitter.

[cjcenizal]

This slightly simplifies the way SearchSource works. I've verified that nothing uses PromiseEmitter or passes a handler to onResults by grepping the codebase and waiting for CI to pass.

[elasticmachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request

[spalger]

I appreciate that this will simplify the SearchSource, but can you please verify that nothing is using PromiseEmitter before removing it? If you did, please include details like that in the description.

[spalger]

Also, by using PromiseEmitter, I more mean relying on the fact that handlers for methods like onResults() are called multiple times. It's possible nothing is even passing a handler to onResults(), but it'd be great to know that type of thing before going into review.

[cjcenizal]

Thanks @spalger! Done.

[spalger]

LGTM! Checked queries in discover, visualize, dashboard, and updates on filter and time range.

Good catch and thanks for doing this. Any opportunity to rip complexity out of the courier is an opportunity we should take.

[jen-huang]

LGTM! Verified that there aren't any other usages of PromiseEmitter or passing a handler to onResults.