Bug 1622012 - [marionette] Read the "marionette.enabled" pref only during startup, and don't allow to change its value. r=marionette-reviewers,maja_zf

Differential Revision: https://phabricator.services.mozilla.com/D67035

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

testing/marionette/components/marionette.js

@@ -306,22 +306,11 @@ class MarionetteParentProcess {
     this.alteredPrefs = new Set();
 
     if (env.exists(ENV_ENABLED)) {
-      MarionettePrefs.enabled = true;
+      this.enabled = true;
+    } else {
+      this.enabled = MarionettePrefs.enabled;
     }
 
-    XPCOMUtils.defineLazyPreferenceGetter(
-      this,
-      "enabled",
-      "marionette.enabled",
-      false,
-      (aPreference, previousValue, newValue) => {
-        if (newValue) {
-          this.init(false);
-        } else {
-          this.uninit();
-        }
-      }
-    );
     Services.ppmm.addMessageListener("Marionette:IsRunning", this);
   }
 
@@ -362,7 +351,7 @@ class MarionetteParentProcess {
         Services.obs.removeObserver(this, topic);
 
         if (!this.enabled && subject.handleFlag("marionette", false)) {
-          MarionettePrefs.enabled = true;
+          this.enabled = true;
         }
 
         // We want to suppress the modal dialog that's shown

testing/marionette/prefs.js

@@ -135,10 +135,6 @@ class MarionetteBranch extends Branch {
     return this.get("enabled", false);
   }
 
-  set enabled(isEnabled) {
-    this.set("enabled", isEnabled);
-  }
-
   /**
    * The `marionette.debugging.clicktostart` preference delays
    * server startup until a modal dialogue has been clicked to allow

testing/marionette/test/unit/test_prefs.js

@@ -119,14 +119,11 @@ add_test(function test_MarionettePrefs_getters() {
 
 add_test(function test_MarionettePrefs_setters() {
   try {
-    MarionettePrefs.enabled = true;
     MarionettePrefs.contentListener = true;
     MarionettePrefs.port = 777;
-    equal(true, MarionettePrefs.enabled);
     equal(true, MarionettePrefs.contentListener);
     equal(777, MarionettePrefs.port);
   } finally {
-    Services.prefs.clearUserPref("marionette.enabled");
     Services.prefs.clearUserPref("marionette.contentListener");
     Services.prefs.clearUserPref("marionette.port");
   }