Adding normal matrix to CSS Shaders

Hi group,

One great outcome of CSS Shader could be the ability to add custom/simple lighting to DOM elements.
The simple addition of the normal matrix to be passed to the shader (as optional),
would allow simple cases without impacting the SPEC too much.

I filed a few more details in the bug below:
https://www.w3.org/Bugs/Public/show_bug.cgi?id=15253

Many thanks,
Fabrice.