Convincing the Chrome (or Firefox, Mathematica, MATLAB, $distro's emacs builds, ...) team to switch to their proprietary gcc/LLVM fork that supports the extensions, I assume.
Proprietary extensions work better in the embedded space, where the status quo is a proprietary toolchain; I doubt you'd be able to get a ton of buy-in from application distributors before you have market dominance.
Fair challenge. I fear though that once a firm gets to say Qualcomm or Apple size in the market then they have the scale to continue to maintain their own fork and develop their own apps with that (e.g. Apple could easily do with Safari etc.)
Proprietary extensions work better in the embedded space, where the status quo is a proprietary toolchain; I doubt you'd be able to get a ton of buy-in from application distributors before you have market dominance.