Bug 1403154 - Don't MOZ_CRASH in PerformanceNavigationTiming::Type if the navigation type is TYPE_RESERVED r=baku

MozReview-Commit-ID: A9lwpjRb3G6

--HG--
extra : rebase_source : 854cc9d8616fa5dc8365c82b1e29a4eab91bb590

dom/performance/PerformanceNavigationTiming.cpp

@@ -83,7 +83,8 @@ PerformanceNavigationTiming::Type()
       return NavigationType::Back_forward;
       break;
     default:
-      MOZ_CRASH(); // Should not happen
+      // The type is TYPE_RESERVED or some other value that was later added.
+      // We fallback to the default of Navigate.
       return NavigationType::Navigate;
   }
 }