* Any state (excluding LOCKED) | ACAMERA_CONTROL_AE_PRECAPTURE_TRIGGER is START | PRECAPTURE | Start AE precapture metering sequence
* Any state (excluding LOCKED) | ACAMERA_CONTROL_AE_PRECAPTURE_TRIGGER is CANCEL| INACTIVE | Currently active precapture metering sequence is canceled</p>
* <p>If the camera device supports AE external flash mode (ON_EXTERNAL_FLASH is included in
* ACAMERA_CONTROL_AE_AVAILABLE_MODES), aeState must be FLASH_REQUIRED after the camera device
* finishes AE scan and it's too dark without flash.</p>
* ACAMERA_CONTROL_AE_AVAILABLE_MODES), ACAMERA_CONTROL_AE_STATE must be FLASH_REQUIRED after
* the camera device finishes AE scan and it's too dark without flash.</p>
* <p>For the above table, the camera device may skip reporting any state changes that happen
* without application intervention (i.e. mode switch, trigger, locking). Any state that
* can be skipped in that manner is called a transient state.</p>