The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2

commit f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2
Author: rtoy <rtoy@chromium.org>
Date: Thu Oct 13 22:14:29 2016

Implement ConstantSourceNode

Add implementation of ConstantSourceNode, including a factory method
and a constructor.

This serves as a very useful constant source node, and, because it has
an AudioParam, it can be used as a constructible AudioParam.

Feature: https://www.chromestatus.com/features/5647701588836352
Intent: https://groups.google.com/a/chromium.org/d/msg/blink-dev/9uoSMZftWfY/GJaqkCUNAAAJ
Spec: https://webaudio.github.io/web-audio-api/#ConstantSourceNode

BUG= 644438 
TEST=constant-source-basic.html, constant-source-output.html

Review-Url: https://codereview.chromium.org/2134813002
Cr-Commit-Position: refs/heads/master@{#425184}

[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/LayoutTests/virtual/stable/webexposed/global-interface-listing-expected.txt
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/LayoutTests/webaudio/audioparam-nominal-range-expected.txt
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/LayoutTests/webaudio/audioparam-nominal-range.html
[add] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/LayoutTests/webaudio/constant-source-basic.html
[add] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/LayoutTests/webaudio/constant-source-onended.html
[add] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/LayoutTests/webaudio/constant-source-output.html
[add] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/LayoutTests/webaudio/constructor/constantsource.html
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/LayoutTests/webexposed/global-interface-listing-expected.txt
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/core/frame/UseCounter.h
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/modules_idl_files.gni
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/webaudio/AudioNode.h
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/webaudio/AudioParam.cpp
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/webaudio/AudioParam.h
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/webaudio/BUILD.gn
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.cpp
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.h
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.idl
[add] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/webaudio/ConstantSourceNode.cpp
[add] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/webaudio/ConstantSourceNode.h
[add] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/webaudio/ConstantSourceNode.idl
[add] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/webaudio/ConstantSourceOptions.idl
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/third_party/WebKit/Source/modules/webaudio/WindowWebAudio.idl
[modify] https://crrev.com/f61f1e00fc29d3e88ef4e3d7b1c63d5b469d92f2/tools/metrics/histograms/histograms.xml