https://bugs.webkit.org/show_bug.cgi?id=85236

Reviewed by Kenneth Russell.

Source/WebCore:

Test: webaudio/oscillator-scheduling.html
to be landed separately to get proper platform baselines

* Modules/webaudio/AudioBufferSourceNode.cpp:
(WebCore::AudioBufferSourceNode::process):
Simplify/remove zeroing-out silence at end of buffer, since it's now handled in the base-class AudioScheduledSourceNode::updateSchedulingInfo().

* Modules/webaudio/AudioContext.cpp:
(WebCore::AudioContext::createBufferSource):
Improve comment about ownership and dynamic-lifetime of AudioBufferSourceNode.

(WebCore::AudioContext::createOscillator):
AudioContext keeps a reference to the Oscillator and that reference is released in AudioScheduledSourceNode,
when it has finished playing.

* Modules/webaudio/AudioScheduledSourceNode.h:
* Modules/webaudio/AudioScheduledSourceNode.cpp:
(WebCore::AudioScheduledSourceNode::updateSchedulingInfo):
updateSchedulingInfo() is now responsible for zeroing out the very start (before a note starts)
and the very end (after note ends) of the output AudioBus.  We've also simplified the number
of arguments passed to this method, because of this. It now handles playbackState transition to FINISHED_STATE.

* Modules/webaudio/Oscillator.cpp:
(WebCore::Oscillator::Oscillator):
(WebCore::Oscillator::calculateSampleAccuratePhaseIncrements):
The frequency value needs to snap immediately to its correct value the very first time.
This bug needs to be fixed here so that the Oscillator layout scheduling test works correctly.

(WebCore::Oscillator::process):
Since Oscillator in now changing to be a AudioScheduledSourceNode, we need to call AudioScheduledSourceNode::updateSchedulingInfo()
to handle playbackState for us.

(WebCore::Oscillator::propagatesSilence):
Add scheduling logic for propagatesSilence().

(Oscillator):
* Modules/webaudio/Oscillator.idl:
Add noteOn(), noteOff() methods and playbackState according to specification.

LayoutTests:

* webaudio/oscillator-scheduling-expected.wav: Added.
* webaudio/resources/oscillator-testing.js:
(generateExponentialOscillatorSweep):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@116201 268f45cc-cd09-0410-ab3c-d52691b4dbfc