Confirmed.

It looks like it doesn't cause a test failure because the RangeError is still created. I will create a Blink-specific test that verifies the actual text of the error so that we can catch this in future.

This is actually a regression introduced in https://codereview.chromium.org/2498983002 M57.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7f4a499745ae9a8601e20ef616e8e1e877934269

commit 7f4a499745ae9a8601e20ef616e8e1e877934269
Author: ricea <ricea@chromium.org>
Date: Tue Jun 13 03:15:21 2017

Streams: Fix exception message for NaN HWM

ReadableStream and WritableStream both used streamErrors.errInvalidHWM
instead of streamErrors.invalidHWM for the message when a strategy
highWaterMark was NaN. This resulted in a RangeError being thrown with
an empty message. Because the web platform tests don't look at the
message, they didn't catch the bug.

Fix the message. Also add a Chromium-specific regression test to
validate that it is correct.

BUG= 719763 

Review-Url: https://codereview.chromium.org/2933853003
Cr-Commit-Position: refs/heads/master@{#478880}

[add] https://crrev.com/7f4a499745ae9a8601e20ef616e8e1e877934269/third_party/WebKit/LayoutTests/http/tests/streams/chromium/err-invalid-hwm.html
[modify] https://crrev.com/7f4a499745ae9a8601e20ef616e8e1e877934269/third_party/WebKit/Source/core/streams/ReadableStream.js
[modify] https://crrev.com/7f4a499745ae9a8601e20ef616e8e1e877934269/third_party/WebKit/Source/core/streams/WritableStream.js