this.settingsKey_=settingsKey;this.maybeInit_();},maybeInit_(){if(!this.needsInit_)return;if(this.settingsKey_===undefined)return;this.needsInit_=false;this.select(tr.b.Settings.get(this.settingsKey_));},set items(items){this.radioButtons_={};items.forEach(function(e){if(e.key in this.radioButtons_){throw new Error(e.key+' already exists');}