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

content/browser/renderer_host/overscroll_controller_delegate.h

Index: content/browser/renderer_host/overscroll_controller_delegate.h
diff --git a/content/browser/renderer_host/overscroll_controller_delegate.h b/content/browser/renderer_host/overscroll_controller_delegate.h
index 0533cde23aae2c6a5b58aae92e628efdeb534b84..97e294bc1cc19569c7305755a69131143fe0e9a4 100644
--- a/content/browser/renderer_host/overscroll_controller_delegate.h
+++ b/content/browser/renderer_host/overscroll_controller_delegate.h
@@ -32,8 +32,12 @@ class CONTENT_EXPORT OverscrollControllerDelegate {
   virtual void OnOverscrollComplete(OverscrollMode overscroll_mode) = 0;
 
   // This is called when the direction of the overscroll changes.
+  // When a new overscroll is started (i.e. when |new_mode| is not
+  // equal to OVERSCROLL_NONE), |source| will be set to the device that
+  // triggered the overscroll gesture.
   virtual void OnOverscrollModeChange(OverscrollMode old_mode,
-                                      OverscrollMode new_mode) = 0;
+                                      OverscrollMode new_mode,
+                                      OverscrollSource source) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OverscrollControllerDelegate);