add: if (!isXPInstallEnabled()) return;  
context:   onDrop: function(aEvent, aXferData, aDragSession)  {    this._ensureServices();        var xpinstallObj = { };    var themes = { };    var xpiCount = 0;    var themeCount = 0;        var count = aDragSession.numDropItems;    for (var i = 0; i < count; ++i) {      var fileData = this._getDataFromDragSession(aDragSession, i);      if (!fileData)        continue;      if (fileData.type == nsIUpdateItem.TYPE_EXTENSION) {        xpinstallObj[fileData.fileName] = fileData.fileURL;        ++xpiCount;      }      else if (fileData.type == nsIUpdateItem.TYPE_THEME) {        themes[fileData.fileName] = fileData.fileURL;        ++themeCount;      }    }    if (xpiCount > 0)       InstallTrigger.install(xpinstallObj);    if (themeCount > 0) {      // XXXrstrong Only allow the install of one theme due to bug 257992      for (var fileName in themes) {        InstallTrigger.installChrome(InstallTrigger.SKIN, themes[fileName], fileName);        break;      }    }  },
meta: 8395	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/8395/e70cc1872d3fa7a9c82c261be41c9d7d67b9d270/extensions.js/clean/toolkit/mozapps/extensions/content/extensions.js