Bug 884750 - Persistent logs options should apply instantly. r=paul

browser/devtools/webconsole/webconsole.js

@@ -383,18 +383,12 @@ WebConsoleFrame.prototype = {
     }.bind(this));
   },
 
-  _persistLog: null,
-
   /**
-   * Getter for the persistent logging preference. This value is cached per
-   * instance to avoid reading the pref too often.
+   * Getter for the persistent logging preference.
    * @type boolean
    */
   get persistLog() {
-    if (this._persistLog === null) {
-      this._persistLog = Services.prefs.getBoolPref(PREF_PERSISTLOG);
-    }
-    return this._persistLog;
+    return Services.prefs.getBoolPref(PREF_PERSISTLOG);
   },
 
   /**