Made the NavigationTracingObserver always be active whenever background tracing is active

chrome/browser/tracing/navigation_tracing.h

Index: chrome/browser/tracing/navigation_tracing.h
diff --git a/chrome/browser/tracing/navigation_tracing.h b/chrome/browser/tracing/navigation_tracing.h
index 80835caaa8f0833027d33f30ef8f6bd319ae028c..2e02fd4cc3747d618ab46dba5bbb5d6ea56dc8de 100644
--- a/chrome/browser/tracing/navigation_tracing.h
+++ b/chrome/browser/tracing/navigation_tracing.h
@@ -16,6 +16,9 @@ void SetupNavigationTracing();
 class NavigationTracingObserver
     : public content::WebContentsObserver,
       public content::WebContentsUserData<NavigationTracingObserver> {
+ public:
+  static bool IsEnabled();
+
  private:
   friend class content::WebContentsUserData<NavigationTracingObserver>;