askOnlyOnce_description=If a page tries to access the <canvas>-API several times a confirm message will appear every time. This switch tries to make only one confirmation. Never the less on some pages there will be more.
allowPDFCanvas_description=The native pdf.js uses <canvas> to display the PDF content. If this is unchecked there will lots of annoying ask dialogs or the PDF display will not work.
askForPermission=Do you want to allow the red bordered <canvas>?
askForInvisiblePermission=Do you want to allow an invisibe <canvas>?