I don't know about Flash, but I'd say this is a bit unlikely. You need special shader programs for custom antialiasing tricks like FXAA.

For WebGL, you should be able to write the shaders and a multi-pass renderer framework that does the antialiasing. However, with WebGL, you're constrained to using somewhat simpler texture formats than you have available with a modern desktop. If you have to use 8 bit RGBA textures, you will probably suffer from color banding and other nasty artifacts compared to 16 bit floating point textures that are normally used on the desktop.