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

content/browser/web_contents/aura/overscroll_navigation_overlay.h

Index: content/browser/web_contents/aura/overscroll_navigation_overlay.h
diff --git a/content/browser/web_contents/aura/overscroll_navigation_overlay.h b/content/browser/web_contents/aura/overscroll_navigation_overlay.h
index a3ea6c0eb2df85b67ac0a5272146b2c95e0235ae..44739c973829be484938104ca6419fcff6e8be6a 100644
--- a/content/browser/web_contents/aura/overscroll_navigation_overlay.h
+++ b/content/browser/web_contents/aura/overscroll_navigation_overlay.h
@@ -32,8 +32,6 @@ class CONTENT_EXPORT OverscrollNavigationOverlay
     : public WebContentsObserver,
       public OverscrollWindowAnimation::Delegate {
  public:
-  // Note that this enum is used to back an UMA histogram, so it should be
-  // treated as append-only.
   enum NavigationDirection { NONE, FORWARD, BACK, NAVIGATION_COUNT };
 
   OverscrollNavigationOverlay(WebContentsImpl* web_contents,
@@ -49,6 +47,9 @@ class CONTENT_EXPORT OverscrollNavigationOverlay
   FRIEND_TEST_ALL_PREFIXES(OverscrollNavigationOverlayTest, WithScreenshot);
   FRIEND_TEST_ALL_PREFIXES(OverscrollNavigationOverlayTest, WithoutScreenshot);
   FRIEND_TEST_ALL_PREFIXES(OverscrollNavigationOverlayTest, CannotNavigate);
+  FRIEND_TEST_ALL_PREFIXES(OverscrollNavigationOverlayTest, ForwardNavigation);
+  FRIEND_TEST_ALL_PREFIXES(OverscrollNavigationOverlayTest,
+                           ForwardNavigationCancelled);
   FRIEND_TEST_ALL_PREFIXES(OverscrollNavigationOverlayTest, CancelNavigation);
   FRIEND_TEST_ALL_PREFIXES(OverscrollNavigationOverlayTest,
                            CancelAfterSuccessfulNavigation);