Fix requestDevice() being called twice
Fix requestDevice() being called twice

Requesting the same HID device twice would cause two DictationDevices to
be created using the same HID device. This would cause all sorts of
errors and weirdness.
We now check if the HID device is already known to us and skip it in
that case.

GoogleChromeLabs/dictation_support,GoogleChromeLabs/dictation_support,GoogleChromeLabs/dictation_support