When putting app to background with qr scanner active, then moved to foreground again,
SimpleScannerActivity instance is not destroyed, but the local mScannerView was re-initialized
with a new instance (through startCamera()) regardless of pre-existing instance, and added to
the contentFrame. This leaves the previous mScannerView instance in limbo, potentially getting
garbage collected at unpredictable times.
Sander van Grieken
3947733d9f