Save audio metadata, after extraction

Fixes #260

renderer/lib/location-history.js

@@ -19,6 +19,7 @@ LocationHistory.prototype._go = function (page) {
     this._pending = page
     page.onbeforeload((err) => {
       if (err) return
+      if (this._pending !== page) return /* navigation was cancelled */
       this._pending = null
       this._history.push(page)
     })
@@ -67,3 +68,7 @@ LocationHistory.prototype.hasForward = function () {
 LocationHistory.prototype.pending = function () {
   return this._pending
 }
+
+LocationHistory.prototype.clearPending = function () {
+  this._pending = null
+}