"crypto/rsa" SignPKCS1v15() completes in about 0.01 second on non-gopherjs x86_64 but 3 seconds in gopherjs on the same machine, which is 300 times slower. Can we do better? This affects things like macgyver's ChromeStorageBackend[1].

Test code/instructions here: https://github.com/idupree/slow-gopherjs-crypto

[1] https://github.com/stripe/macgyver