[iOS] Add UserAction when the doodle is tapped

This can be useful for breadcrumbs or other metrics purpose.

Added on crrev.com/i/3115706.

Bug: 1082908
Change-Id: Ide69472a86d42276bcee9049eb90ef3bdf2a1bea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2241129
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Auto-Submit: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#778850}

tools/metrics/actions/actions.xml

@@ -8602,6 +8602,18 @@ 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="IOS.NTP.Doodle.Tapped">
+  <owner>gambard@chromium.org</owner>
+  <owner>justincohen@chromium.org</owner>
+  <description>
+    Recorded when the user is tapping the doodle on the NTP. There is also a
+    histogram (NewTabPageActioniOS::doodle), but histograms are not recorded in
+    Breadcrumbs. iOS Breadcrumbs attaches steps the user performed in the app to
+    crash logs. These steps can help debug causes of crashes when the stack
+    doesn't provide enough information.
+  </description>
+</action>
+
 <action name="IOS.PageZoom.ZoomIn">
   <owner>rkgibson@google.com</owner>
   <owner>gambard@chromium.org</owner>