Bug 1545410 - part 2: Add telemetry probe to decide when we can remove the hack for Office Online Server data-review=liuche, r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D32288

--HG--
extra : moz-landing-system : lando

toolkit/actors/KeyPressEventModelCheckerChild.jsm

@@ -39,12 +39,17 @@ class KeyPressEventModelCheckerChild extends ActorChild {
   _isOldOfficeOnlineServer(aDocument) {
     let editingElement =
         aDocument.getElementById("WACViewPanel_EditingElement");
+    // If it's not Office Online Server, don't include it into the telemetry
+    // because we just need to collect percentage of old version in all loaded
+    // Office Online Server instances.
     if (!editingElement) {
       return false;
     }
     let isOldVersion =
         !editingElement.classList.contains(
             "WACViewPanel_DisableLegacyKeyCodeAndCharCode");
+    Services.telemetry.keyedScalarAdd("dom.event.office_online_load_count",
+                                      isOldVersion ? "old" : "new", 1);
     return isOldVersion;
   }
 

toolkit/components/telemetry/Scalars.yaml

@@ -1981,6 +1981,23 @@ dom.event:
     record_in_processes:
       - 'content'
 
+  office_online_load_count:
+    bug_numbers:
+      - 1545410
+    description: >
+      Number of times Office Online Server instances are loaded, and whether
+      they are compatible with conflated keypress event model or not, using
+      "new"/"old".  I.e., collecting percentage of too old Confluence instance
+      use count in all Office Online Server instance use count.
+    expires: "71"
+    keyed: true
+    kind: uint
+    notification_emails:
+      - mnakano@mozilla.com
+    release_channel_collection: opt-out
+    record_in_processes:
+      - 'content'
+
 navigator.storage:
   estimate_count:
     bug_numbers: