stream: simplify checks for highWaterMark

[mcollina]

• Version: master
• Platform: all
• Subsystem: stream

In lib/_streams_readable.js, we have a block of code like this:

          (state.length < state.highWaterMark ||
           state.length === 0);

Because state.highWaterMark  could be < 0 or null or undefined or really any object in Node < 10. However, we landed #18098 and so now we can simplify all those checks to be state.length <= state.highWaterMark.

[dicearr]

So line lib/_streams_readable.js#314 and line lib/_streams_readable.js#437 needs to be replaced. Removing state.length === 0 and replacing < with <=. Am I right?

[sagirk]

@mcollina If no one is already working on this, I would like to volunteer. First-time node contributor.

[vishal7201]

@sagirk I have started working on the issue

[bakpatrycja]

i also have started to work on it

[kodemill]

@mcollina @vishal7201 I made some progress on this, since it looked like it was orphaned.
@RoGalinka sorry, I just missed your comment.