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[Public WebGL] ANGLE_instanced_arrays extension proposal

I've just added a proposal for adding ANGLE_instanced_arrays to WebGL to allow geometry instancing:

This extension is a stripped-down version of ARB_instanced_arrays that can be easily-implemented on top of Direct3D 9.

It can be used by setting a divisor, n, on certain vertex attribs. Then when drawing multiple instances of a certain piece of geometry, those vertex attributes will keep the same value for every vertex in an entire instance. After drawing n instances, it will move on to the next value for that attrib.

Desktop support:
 - All Direct3D 9 hardware with Shader Model 3.0 supports it
 - Supported through ANGLE on windows.
 - Supported on OS X Lion on all machines, and on Snow Leopard on most machines
 - Supported on NVIDIA's linux drivers, and probably ATI's

Mobile support:
This is more difficult, as no mobile device that I know of supports geometry instancing. This could be supported using pseudo-instancing, but that would require either keeping a shadow copy of every vertex buffer in case it's used as instanced data, or performing a complicated and expensive readback to get at that data.

Does this seem like a worthwhile extension to people?