1. Attempt an empty password every time a keystore is uploaded.
2. Delegate scrypt decryption (ie ethereumjs-wallet.fromV3) to its own web worker and interface with it through an async typescript function that gets handled in the wallet saga. This keeps the UI unblocked when scrypt takes a long time to decrypt.
3. Add logic to show a spinner x number of milliseconds after file upload so the user will understand when a wallet is being decrypted.
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