Added direct JavaScript processing to WebKit prototype

I've implemented a JavaScriptAudioNode in the WebKit audio branch and
created a working demo for it which I put on the demo page:
http://chromium.googlecode.com/svn/trunk/samples/audio/index.html

Here's the direct link to this new demo:
http://chromium.googlecode.com/svn/trunk/samples/audio/javascript-processing.html

The new demo is called "JavaScript Processing" and illustrates a simple
amplitude modulation effect, with a WebGL visualizer to look at the side
lobes as they move around.  As with all the demos, it requires a special
build of WebKit to run with Safari or Chrome (build instructions on the demo
page).  But, of course, you can always "view source" without running it...

I'm hoping to post binaries soon for Safari and Chrome so people don't have
to build for themselves, but I've been busy working on the direct JavaScript
processing and other stuff in the past week or so.  Also, soon I'll update
my specification proposal to include an initial API for this
JavaScriptAudioNode which will be very similar to what we've discussed
recently on this list.

This demo is pretty simple, but I'd be very interested in porting some of
the Mozilla demos to this API.  Corban, would it be OK with you if I ported
some of your demos which use the DSP.js library you've been working on?

Cheers,
Chris