18/02/05 22:06:31.27 VP2+0v330.net
文字列を送る・消すを一つにまとめ、コードも簡略化しました
var selmM = gBrowser.selectedBrowser.messageManager;
selmM.addMessageListener('getSelection', function listener(message) {
var txtbox = document.getElementById('searchbar').textbox;
var selection = message.data;
if(selection) txtbox.value = selection;
else txtbox.value = "";
});
selmM.loadFrameScript('data:,sendAsyncMessage("getSelection", content.document.getSelection().toString())', true);