These APIs are standardized and should be in the AudioContext and not BaseAudioContext.  We can't move these quite yet because we depend on being able to test these using an OfflineAudioContext.

Should we standardize them in BaseAudioContext in stead then? 

No, that doesn't really make sense there because offline context run faster than real time and because CORS will prevent many uses of them because an offline context lets you get at the audio data.

This is something we need to fix but we need to get our layout tests running on bots have have real audio hardware.

If this is needed for our own testing, is there a sensible use case for web developers as well? Or is this taking some test-only code path that doesn't actually work in the end-user binary?

I think it's useful to have these on an offline context, but we never bothered to explain how that would work when the offline context can run much faster than real time and pulling on an audio tag faster than real time.

Currently, there is not test-only code path for these methods; it should work for anyone, taking into account the behavior isn't well-defined.

Does it currently cause the offline audio context to run slower, at wall clock time?

Never really tested this except in the layout test which has a pretty short wav file.  I'll have to try it out and see what happens.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2ea3396c11d748579c305232a5306c0ad498e616

commit 2ea3396c11d748579c305232a5306c0ad498e616
Author: Joshua Bell <jsbell@chromium.org>
Date: Mon Mar 19 21:49:59 2018

Web Platform Tests: add /interfaces/webaudio.idl and corresponding test

The Web Audio tests (in /webaudio) have idlharness test on an
interface-by-interface basis, but the new hotness is to have the
IDL fragments consolidated. This also allows dependent specs to
include the master interface definitions.

Bug: 679813, 697123 ,785409, 823431 

Change-Id: I60bc8415627b8b3f43c13060e4bf65f47bc17c2b
Reviewed-on: https://chromium-review.googlesource.com/965401
Commit-Queue: Joshua Bell <jsbell@chromium.org>
Reviewed-by: Raymond Toy <rtoy@chromium.org>
Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544173}
[add] https://crrev.com/2ea3396c11d748579c305232a5306c0ad498e616/third_party/WebKit/LayoutTests/external/wpt/interfaces/webaudio.idl
[add] https://crrev.com/2ea3396c11d748579c305232a5306c0ad498e616/third_party/WebKit/LayoutTests/external/wpt/webaudio/idlharness.https-expected.txt
[add] https://crrev.com/2ea3396c11d748579c305232a5306c0ad498e616/third_party/WebKit/LayoutTests/external/wpt/webaudio/idlharness.https.html

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/79cb0630cf6ad293e913124fe0f51872a587005b

commit 79cb0630cf6ad293e913124fe0f51872a587005b
Author: Raymond Toy <rtoy@chromium.org>
Date: Fri Oct 05 21:50:00 2018

Move Media nodes to AudioContext

The Media nodes should be on the AudioContext, not BaseAudioContext.
Make it so.  This also implies that the constructors for these nodes
should take an AudioContext, not BaseAudioContext.

Intent: https://groups.google.com/a/chromium.org/d/msg/blink-dev/H29uXnsIN54/BKXDqxoJAQAJ
Chrome feature entry: https://www.chromestatus.com/feature/5258622686724096

Bug:  845913 ,  842225 ,  697123 
Change-Id: Ic2a82a2343fa4a169a26733375c646fec61769ed
Reviewed-on: https://chromium-review.googlesource.com/c/1069692
Commit-Queue: Raymond Toy <rtoy@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597322}
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/content/test/data/media/mediarecorder_test.html
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/WebKit/LayoutTests/external/wpt/webaudio/idlharness.https-expected.txt
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/WebKit/LayoutTests/external/wpt/webaudio/idlharness.https.window-expected.txt
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/WebKit/LayoutTests/virtual/stable/webexposed/global-interface-listing-expected.txt
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/WebKit/LayoutTests/webaudio/AudioParam/audioparam-nominal-range-expected.txt
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/WebKit/LayoutTests/webaudio/AudioParam/audioparam-nominal-range.html
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/WebKit/LayoutTests/webaudio/MediaStreamAudioDestination/ctor-mediastreamaudiodestination.html
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/WebKit/LayoutTests/webaudio/MediaStreamAudioSource/ctor-mediastreamaudiosource.html
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/WebKit/LayoutTests/webaudio/dom-exceptions-expected.txt
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/WebKit/LayoutTests/webexposed/global-interface-listing-expected.txt
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/audio_context.cc
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/audio_context.h
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/audio_context.idl
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/base_audio_context.cc
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/base_audio_context.h
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/base_audio_context.idl
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/media_element_audio_source_node.cc
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/media_element_audio_source_node.h
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/media_element_audio_source_node.idl
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/media_stream_audio_destination_node.cc
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/media_stream_audio_destination_node.h
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/media_stream_audio_destination_node.idl
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/media_stream_audio_source_node.cc
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/media_stream_audio_source_node.h
[modify] https://crrev.com/79cb0630cf6ad293e913124fe0f51872a587005b/third_party/blink/renderer/modules/webaudio/media_stream_audio_source_node.idl