Add User Actions and adding more details to UMA metrics for overscroll navigation

content/browser/web_contents/aura/overscroll_window_delegate.h

Index: content/browser/web_contents/aura/overscroll_window_delegate.h
diff --git a/content/browser/web_contents/aura/overscroll_window_delegate.h b/content/browser/web_contents/aura/overscroll_window_delegate.h
index 1abde586930fd5e51216aca95ca95a83ab078018..f267b851277a9d6446443179c933dd7ebced6213 100644
--- a/content/browser/web_contents/aura/overscroll_window_delegate.h
+++ b/content/browser/web_contents/aura/overscroll_window_delegate.h
@@ -29,7 +29,7 @@ class CONTENT_EXPORT OverscrollWindowDelegate
   ~OverscrollWindowDelegate() override;
 
   // Starts the overscroll gesture.
-  void StartOverscroll();
+  void StartOverscroll(OverscrollSource source);
 
   // Resets the overscroll state.
   void ResetOverscroll();
@@ -38,7 +38,7 @@ class CONTENT_EXPORT OverscrollWindowDelegate
   void CompleteOrResetOverscroll();
 
   // Updates the current horizontal overscroll.
-  void UpdateOverscroll(float delta_x);
+  void UpdateOverscroll(float delta_x, OverscrollSource source);
 
   // Overridden from ui::EventHandler.
   void OnKeyEvent(ui::KeyEvent* event) override;