Bug 1620244 - Retention telemetry for HTTPS Only Mode. r=ckerschb,jcj

Differential Revision: https://phabricator.services.mozilla.com/D69547

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

browser/components/BrowserGlue.jsm

@@ -1970,6 +1970,26 @@ BrowserGlue.prototype = {
     });
   },
 
+  _monitorHTTPSOnlyPref() {
+    const PREF_ENABLED = "dom.security.https_only_mode";
+    const PREF_WAS_ENABLED = "dom.security.https_only_mode_ever_enabled";
+    const _checkHTTPSOnlyPref = async () => {
+      const enabled = Services.prefs.getBoolPref(PREF_ENABLED, false);
+      const was_enabled = Services.prefs.getBoolPref(PREF_WAS_ENABLED, false);
+      let value = 0;
+      if (enabled) {
+        value = 1;
+        Services.prefs.setBoolPref(PREF_WAS_ENABLED, true);
+      } else if (was_enabled) {
+        value = 2;
+      }
+      Services.telemetry.scalarSet("security.https_only_mode_enabled", value);
+    };
+
+    Services.prefs.addObserver(PREF_ENABLED, _checkHTTPSOnlyPref);
+    _checkHTTPSOnlyPref();
+  },
+
   _showNewInstallModal() {
     // Allow other observers of the same topic to run while we open the dialog.
     Services.tm.dispatchToMainThread(() => {
@@ -2057,6 +2077,7 @@ BrowserGlue.prototype = {
 
     this._monitorScreenshotsPref();
     this._monitorWebcompatReporterPref();
+    this._monitorHTTPSOnlyPref();
 
     let pService = Cc["@mozilla.org/toolkit/profile-service;1"].getService(
       Ci.nsIToolkitProfileService

modules/libpref/init/StaticPrefList.yaml

@@ -2454,6 +2454,14 @@
   value: false
   mirror: always
 
+# WARNING: Don't ever update that pref manually! It is only used
+# for telemetry purposes and allows to reason about retention of
+# the pref dom.security.https_only_mode from above.
+- name: dom.security.https_only_mode_ever_enabled
+  type: RelaxedAtomicBool
+  value: false
+  mirror: always
+
 # Is support for selection event APIs enabled?
 - name: dom.select_events.enabled
   type: bool

toolkit/components/telemetry/Scalars.yaml

@@ -758,6 +758,21 @@ security:
       - 'geckoview'
     record_in_processes:
       - main
+  https_only_mode_enabled:
+    bug_numbers:
+      - 1620244
+    description: >
+      Measures user retention of the HTTPS-Only Mode.
+      0 = never enabled, 1 = enabled, 2 = disabled (but was enabled)
+    expires: never
+    kind: uint
+    notification_emails:
+      - julianwels@mozilla.com
+      - seceng-telemetry@mozilla.com
+    products:
+      - 'firefox'
+    record_in_processes:
+      - 'main'
 
 pwmgr:
   potentially_breached_passwords: