Test config for the feed header menu iph feature

Bug: 1095106
Change-Id: Iffd8a1645e60ee2f02a69f8c5ac2b823aaf57fb0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2246848Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Vincent Boisselle <vincb@google.com>
Cr-Commit-Position: refs/heads/master@{#778618}

testing/variations/fieldtrial_testing_config.json

@@ -2585,6 +2585,12 @@
             "experiments": [
                 {
                     "name": "Enaled",
+                    "params": {
+                        "availability": "any",
+                        "event_trigger": "name:iph_feed_header_menu_triggered;comparator:==0;window:360;storage:360",
+                        "event_used": "name:feed_header_menu_clicked;comparator:==0;window:360;storage:360",
+                        "session_rate": "==0"
+                    },
                     "enable_features": [
                         "IPH_FeedHeaderMenu",
                         "ReportFeedUserActions"