Optional: if an engine supports the pause event, it should pause the
current utterance being spoken, if any, until it receives a resume event
or stop event. Note that a stop event should also clear the paused state.
Optional: if an engine supports the pause event, it should also support
the resume event, to continue speaking the current utterance, if any. Note
that a stop event should also clear the paused state.
Called when the user makes a call to tts.speak() and one of the voices
from this extension's manifest is the first to match the options object.
Differs from ttsEngine.onSpeak in that Chrome provides audio playback
services and handles dispatching tts events.
Fired when a call is made to tts.stop and this extension may be in the
middle of speaking. If an extension receives a call to onStop and speech
is already stopped, it should do nothing (not raise an error). If speech
is in the paused state, this should cancel the paused state.
Called by an engine to update its list of voices. This list overrides any
voices declared in this extension's manifest.
voices Array of tts.TtsVoice objects representing the available
voices for speech synthesis.