stream: reset awaitDrain after manual .resume()

Reset the `readableState.awaitDrain` counter after manual calls to
`.resume()`.

What might happen otherwise is that a slow consumer at the end of the
pipe could end up stalling the piping in the following scenario:

1. The writable stream indicates that its buffer is full.
2. This leads the readable stream to `pause()` and increase its
   `awaitDrain` counter, which will be decreased by the writable’s next
   `drain` event.
3. Something calls `.resume()` manually.
4. The readable continues to pipe to the writable, but once again
   the writable stream indicates that the buffer is full.
5. The `awaitDrain` counter is thus increased again, but since it has
   now been increased twice for a single piping destination, the next
   `drain` event will not be able to reset `awaitDrain` to zero.
6. The pipe is stalled and no data is passed along anymore.

The solution in this commit is to reset the `awaitDrain` counter to
zero when `resume()` is called.

Fixes: https://github.com/nodejs/node/issues/7159
PR-URL: https://github.com/nodejs/node/pull/7160
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

0 files changed, 0 insertions, 0 deletions