The error message

"This readable stream reader has been released and cannot be used to monitor the stream's state"

is defined In ReadableStream.js as errReleasedReaderClosedPromise. It's saying you can't use |reader.closed| from now on as |reader| detached. WAI? Or should we suppress the uncaught-rejection somehow?

I guess we should suppress it. We can just do

thenPromise(reader[readableStreamReaderClosedPromise], undefined, () => {})

to do this, or maybe add a simpler API to V8 extras that sets [[PromiseIsHandled]]. Maybe we should do this more generally, with a spec change. I will open a spec issue.

https://github.com/whatwg/streams/issues/547

Waiting for resolution in the Streams Standard.

The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/2f060955e881aad0e6d5124c533403d3b172bb3b

commit 2f060955e881aad0e6d5124c533403d3b172bb3b
Author: domenic <domenic@chromium.org>
Date: Tue Nov 15 21:24:58 2016

Add markPromiseAsHandled V8 extra util

This will allow V8 extra consumers to mark a promise as handled without
adding redundant empty onRejected handlers. This is needed by streams as
discussed in https://github.com/whatwg/streams/issues/547.

BUG= chromium:654701 

Review-Url: https://codereview.chromium.org/2498143002
Cr-Commit-Position: refs/heads/master@{#41012}

[modify] https://crrev.com/2f060955e881aad0e6d5124c533403d3b172bb3b/src/js/promise.js
[modify] https://crrev.com/2f060955e881aad0e6d5124c533403d3b172bb3b/test/cctest/test-api.cc
[modify] https://crrev.com/2f060955e881aad0e6d5124c533403d3b172bb3b/test/cctest/test-extra.js

Resolved in the Streams standard. Taking ownership. I need to fix this before the change to testharness.js which makes unhandled promises an error.

The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/2f060955e881aad0e6d5124c533403d3b172bb3b

commit 2f060955e881aad0e6d5124c533403d3b172bb3b
Author: domenic <domenic@chromium.org>
Date: Tue Nov 15 21:24:58 2016

Add markPromiseAsHandled V8 extra util

This will allow V8 extra consumers to mark a promise as handled without
adding redundant empty onRejected handlers. This is needed by streams as
discussed in https://github.com/whatwg/streams/issues/547.

BUG= chromium:654701 

Review-Url: https://codereview.chromium.org/2498143002
Cr-Commit-Position: refs/heads/master@{#41012}

[modify] https://crrev.com/2f060955e881aad0e6d5124c533403d3b172bb3b/src/js/promise.js
[modify] https://crrev.com/2f060955e881aad0e6d5124c533403d3b172bb3b/test/cctest/test-api.cc
[modify] https://crrev.com/2f060955e881aad0e6d5124c533403d3b172bb3b/test/cctest/test-extra.js

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/88ec71ef1d62b1719e0e7dc35e18ae21e02d2f8c

commit 88ec71ef1d62b1719e0e7dc35e18ae21e02d2f8c
Author: domenic <domenic@chromium.org>
Date: Wed Dec 21 15:13:19 2016

Mark readable stream closed promise as handled

This matches the spec update at https://github.com/whatwg/streams/commit/0745219ca7b7f02ef104145b78ebebd99c0fd12c for readable streams. The remaining work for writable streams will be performed as part of https://bugs.chromium.org/p/chromium/issues/detail?id=671958.

BUG= 654701 
TEST=will be tested by the updated expectations in https://codereview.chromium.org/2500133002

Review-Url: https://codereview.chromium.org/2588983002
Cr-Commit-Position: refs/heads/master@{#440101}

[modify] https://crrev.com/88ec71ef1d62b1719e0e7dc35e18ae21e02d2f8c/third_party/WebKit/Source/core/streams/ReadableStream.js