The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1ef23c62889c7c9fa4c93999a364c6939bf4da92

commit 1ef23c62889c7c9fa4c93999a364c6939bf4da92
Author: rtoy <rtoy@chromium.org>
Date: Tue Aug 01 16:09:41 2017

Make AudioBufferSourceNode.buffer setter conforming

Make ABSN.buffer setter conform to the spec.  We were already throwing
errors on attempts to set the buffer twice.  To conform, we need to
allow setting the buffer to null, but still throwing an error if the
buffer was ever set to a non-null value.

BUG=591089
TEST=AudioBufferSource/audiobuffersource-channels.html

Review-Url: https://codereview.chromium.org/2842003003
Cr-Commit-Position: refs/heads/master@{#491003}

[modify] https://crrev.com/1ef23c62889c7c9fa4c93999a364c6939bf4da92/third_party/WebKit/LayoutTests/webaudio/AudioBufferSource/audiobuffersource-channels.html
[modify] https://crrev.com/1ef23c62889c7c9fa4c93999a364c6939bf4da92/third_party/WebKit/LayoutTests/webaudio/dom-exceptions-expected.txt
[modify] https://crrev.com/1ef23c62889c7c9fa4c93999a364c6939bf4da92/third_party/WebKit/Source/modules/webaudio/AudioBufferSourceNode.cpp
[modify] https://crrev.com/1ef23c62889c7c9fa4c93999a364c6939bf4da92/third_party/WebKit/Source/modules/webaudio/AudioBufferSourceNode.h
[modify] https://crrev.com/1ef23c62889c7c9fa4c93999a364c6939bf4da92/third_party/WebKit/Source/modules/webaudio/AudioBufferSourceNode.idl