https://github.com/WebAudio/web-audio-api/pull/1057 has landed.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ba258a3d5e041db72953fd72f19e78747ef74602

commit ba258a3d5e041db72953fd72f19e78747ef74602
Author: rtoy <rtoy@chromium.org>
Date: Tue Dec 06 18:13:43 2016

Add constructors for WebAudio events

Add constructor for WebAudio AudioProcessingEvent and
OfflineAudioCompletionEvent.

Intent: https://groups.google.com/a/chromium.org/d/msg/blink-dev/G3V0F7Rh0Io/MuLBeUZeAQAJ

BUG= 662164 
TEST=event-constructor.html

Review-Url: https://codereview.chromium.org/2491653002
Cr-Commit-Position: refs/heads/master@{#436647}

[add] https://crrev.com/ba258a3d5e041db72953fd72f19e78747ef74602/third_party/WebKit/LayoutTests/webaudio/event-constructor.html
[modify] https://crrev.com/ba258a3d5e041db72953fd72f19e78747ef74602/third_party/WebKit/Source/modules/modules_idl_files.gni
[modify] https://crrev.com/ba258a3d5e041db72953fd72f19e78747ef74602/third_party/WebKit/Source/modules/webaudio/AudioProcessingEvent.cpp
[modify] https://crrev.com/ba258a3d5e041db72953fd72f19e78747ef74602/third_party/WebKit/Source/modules/webaudio/AudioProcessingEvent.h
[modify] https://crrev.com/ba258a3d5e041db72953fd72f19e78747ef74602/third_party/WebKit/Source/modules/webaudio/AudioProcessingEvent.idl
[add] https://crrev.com/ba258a3d5e041db72953fd72f19e78747ef74602/third_party/WebKit/Source/modules/webaudio/AudioProcessingEventInit.idl
[modify] https://crrev.com/ba258a3d5e041db72953fd72f19e78747ef74602/third_party/WebKit/Source/modules/webaudio/OfflineAudioCompletionEvent.cpp
[modify] https://crrev.com/ba258a3d5e041db72953fd72f19e78747ef74602/third_party/WebKit/Source/modules/webaudio/OfflineAudioCompletionEvent.h
[modify] https://crrev.com/ba258a3d5e041db72953fd72f19e78747ef74602/third_party/WebKit/Source/modules/webaudio/OfflineAudioCompletionEvent.idl
[add] https://crrev.com/ba258a3d5e041db72953fd72f19e78747ef74602/third_party/WebKit/Source/modules/webaudio/OfflineAudioCompletionEventInit.idl