stream: prevent object map change in ReadableState

stream: prevent object map change in ReadableState

ReadableState has the resumeScheduled property that helps determine if
a stream should be resumed. It was not assigned in the constructor.
When stream.resume is called on a readable stream that is not flowing,
it is set to true. This changes the property map of the ReadableState
which can cause a deopt in onEofChunk and needMoreData.

PR-URL: https://github.com/nodejs/node/pull/4761
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>