Merge "Docs: generateKeyPair() can't be called from the main thread."

     * Called by a device or profile owner, or delegated certificate installer, to generate a

     * new private/public key pair. If the device supports key generation via secure hardware,

     * this method is useful for creating a key in KeyChain that never left the secure hardware.

     *

     * Access to the key is controlled the same way as in {@link #installKeyPair}.

     *

     * <p>Because this method might take several seconds to complete, it should only be called from

     * a worker thread. This method returns {@code null} when called from the main thread.

     *

     * @param admin Which {@link DeviceAdminReceiver} this request is associated with, or

     *            {@code null} if calling from a delegated certificate installer.

     * @param algorithm The key generation algorithm, see {@link java.security.KeyPairGenerator}.