Moving forward from nightly.variables.toolkit == "cairo"

toolkit.js

const { classes: Cc, interfaces: Ci, utils: Cu } = Components; 
var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo); gfxInfo.getInfo().toSource();
/**
 * Example output:
 * ({AzureCanvasBackend:"cairo", AzureFallbackCanvasBackend:"none", AzureContentBackend:"none"})
 *
 * Or:
 * Error: gfxInfo.getInfo is not a function
 *
 * Or even:
 * Error: Cc['@mozilla.org/gfx/info;1'] is undefined
 */