Bug 1785322 - Add a use comment to remind people that new use-counters need data-r. r=saschanaz DONTBUILD

Differential Revision: https://phabricator.services.mozilla.com/D154933

dom/base/UseCounters.conf

@@ -34,6 +34,9 @@
 // annotating things with [UseCounter] in the relevant WebIDL file as
 // well.  Generating things from bindings codegen and ensuring all the
 // dependencies were correct would have been rather difficult.
+//
+// NOTE: Adding use counters requires data review, see
+// https://wiki.mozilla.org/Data_Collection
 
 method SVGSVGElement.getElementById
 attribute SVGSVGElement.currentScale
@@ -400,3 +403,6 @@ method Element.setHTML
 
 // Features that might be deprecated in the future
 custom WindowOpenEmptyUrl calls window.open with an empty url argument
+
+// NOTE: Adding use counters requires data review, see
+// https://wiki.mozilla.org/Data_Collection