Changes PlzNavitate histograms to try and simplify their multi-modal characteristic.

content/browser/frame_host/navigator.h

Index: content/browser/frame_host/navigator.h
diff --git a/content/browser/frame_host/navigator.h b/content/browser/frame_host/navigator.h
index b05b538a2114c1a47ba7a31046d6ce8a424dd1f5..229918cced195f5dbea7b439d3c41630d8610382 100644
--- a/content/browser/frame_host/navigator.h
+++ b/content/browser/frame_host/navigator.h
@@ -139,6 +139,12 @@ class CONTENT_EXPORT Navigator : public base::RefCounted<Navigator> {
   virtual void LogResourceRequestTime(
     base::TimeTicks timestamp, const GURL& url) {};
 
+  // Called to record the time it took to execute the before unload hook for the
+  // current navigation.
+  virtual void LogBeforeUnloadTime(
+    const base::TimeTicks& renderer_before_unload_start_time,
+    const base::TimeTicks& renderer_before_unload_end_time) {}
+
  protected:
   friend class base::RefCounted<Navigator>;
   virtual ~Navigator() {}