Heap-use-after-free in WebCore::AudioNodeInput::updateInternalBus
https://bugs.webkit.org/show_bug.cgi?id=108542

Replace the wrong AudioNodeOutput::bus() usage out of safe peroid,
which causes this issue.

Reviewed by Chris Rogers.

* Modules/webaudio/AudioNodeInput.cpp:
(WebCore::AudioNodeInput::numberOfChannels):
* Modules/webaudio/AudioNodeOutput.cpp:
(WebCore::AudioNodeOutput::bus):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144417 268f45cc-cd09-0410-ab3c-d52691b4dbfc