add prefs that devtools assumes will be set

defaults/preferences/devtools-startup-prefs.js

@@ -0,0 +1,39 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This Devtools preferences file will be loaded as a usual Firefox preferences file.
+// Most DevTools prefs are included with the addon and loaded dynamically during the addon
+// startup. For preferences that are required before the addon is loaded or that we can't
+// process in JS, they can be defined in this file.
+// Note that this preference file follows Firefox release cycle.
+
+// Enable the JSON View tool (an inspector for application/json documents).
+pref("devtools.jsonview.enabled", true);
+
+// Default theme ("dark" or "light")
+//@line 18 "/builds/worker/workspace/build/src/devtools/shim/devtools-startup-prefs.js"
+pref("devtools.theme", "light", sticky);
+//@line 20 "/builds/worker/workspace/build/src/devtools/shim/devtools-startup-prefs.js"
+
+// Should the devtools toolbar be opened on startup
+pref("devtools.toolbar.visible", false);
+
+// Pref to drive the devtools onboarding flow experiment. States:
+// - off: forces devtools.enabled to true
+// - on: devtools.enabled is not forced to true.
+// - force: devtools.enabled is not forced to true and cannot be set to true by checking
+//   devtools.selfxss.count. User will have to go through onboarding to use DevTools.
+pref("devtools.onboarding.experiment", "off");
+
+// If devtools.onboarding.experiment is set to "on" or "force", we will flip the
+// devtools.enabled preference to false once. The flag is used to make sure it is only
+// flipped once.
+pref("devtools.onboarding.experiment.flipped", false);
+
+// Flag to check if we already logged the devtools onboarding related probe.
+pref("devtools.onboarding.telemetry.logged", false);
+
+// Completely disable DevTools entry points, as well as all DevTools command line
+// arguments This should be merged with devtools.enabled, see Bug 1440675.
+pref("devtools.policy.disabled", false);