Synchronize setting of panner node model and processing
https://bugs.webkit.org/show_bug.cgi?id=109599

Reviewed by Chris Rogers.

No new tests.

* Modules/webaudio/PannerNode.cpp:
(WebCore::PannerNode::process):
(WebCore::PannerNode::setPanningModel):
* Modules/webaudio/PannerNode.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@142687 268f45cc-cd09-0410-ab3c-d52691b4dbfc