[Extensions Metrics] Records a user action for checkup NTP promo clicks.

This is recorded in addition to the histogram so that we can use the user action sequencing dashboard to see what users do on the chrome://extensions page, and use the histogram to see which messaging is most effective.

Design Doc: http://go/extensionscheckupmetrics

Bug: 1034541
Change-Id: I490eeec2a666e7fac094f7ac0872540c50c0dc8d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2031534Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Archana Simha <archanasimha@chromium.org>
Cr-Commit-Position: refs/heads/master@{#739093}

chrome/browser/ui/search/search_tab_helper.cc

@@ -802,6 +802,7 @@ void SearchTabHelper::OpenExtensionsPage(double button,
                                          bool shift_key) {
   if (!search::DefaultSearchProviderIsGoogle(profile()))
     return;
+  base::RecordAction(base::UserMetricsAction("Extensions.NtpPromoClicked"));
   UMA_HISTOGRAM_ENUMERATION(
       "Extensions.Checkup.NtpPromoClicked",
       static_cast<extensions::CheckupMessage>(

tools/metrics/actions/actions.xml

@@ -5996,6 +5996,15 @@ should be able to be added at any place in this file.
   <description>Please enter the description of this user action.</description>
 </action>
 
+<action name="Extensions.NtpPromoClicked">
+  <owner>archanasimha@chromium.org</owner>
+  <owner>extensions-core@chromium.org</owner>
+  <description>
+    Records every time the user clicks on the extensions checkup middle slot
+    promo link.
+  </description>
+</action>
+
 <action name="Extensions.RemovedDefaultInstalledExtension">
   <owner>archanasimha@chromium.org</owner>
   <description>