--- a/devtools/client/definitions.js
+++ b/devtools/client/definitions.js
@@ -462,16 +462,37 @@ Tools.firebugTheme = {
 };
 
 exports.defaultThemes = [
   Tools.darkTheme,
   Tools.lightTheme,
   Tools.firebugTheme,
 ];
 
+// White-list buttons that can be toggled to prevent adding prefs for
+// addons that have manually inserted toolbarbuttons into DOM.
+// (By default, supported target is only local tab)
+exports.ToolboxButtons = [
+  { id: "command-button-frames",
+    isTargetSupported: target => {
+      return target.activeTab && target.activeTab.traits.frames;
+    }
+  },
+  { id: "command-button-splitconsole",
+    isTargetSupported: target => !target.isAddon },
+  { id: "command-button-responsive" },
+  { id: "command-button-paintflashing" },
+  { id: "command-button-scratchpad" },
+  { id: "command-button-screenshot" },
+  { id: "command-button-rulers" },
+  { id: "command-button-measure" },
+  { id: "command-button-noautohide",
+    isTargetSupported: target => target.chrome },
+];
+
 /**
  * Lookup l10n string from a string bundle.
  *
  * @param {string} name
  *        The key to lookup.
  * @param {string} arg
  *        Optional format argument.
  * @returns A localized version of the given key.

--- a/devtools/client/framework/toolbox.js
+++ b/devtools/client/framework/toolbox.js
@@ -56,43 +56,24 @@ loader.lazyRequireGetter(this, "system",
   "devtools/shared/system");
 loader.lazyRequireGetter(this, "getPreferenceFront",
   "devtools/shared/fronts/preference", true);
 loader.lazyRequireGetter(this, "KeyShortcuts",
   "devtools/client/shared/key-shortcuts", true);
 loader.lazyRequireGetter(this, "ZoomKeys",
   "devtools/client/shared/zoom-keys");
 loader.lazyRequireGetter(this, "settleAll",
-  "devtools/shared/ThreadSafeDevToolsUtils", "settleAll");
+  "devtools/shared/ThreadSafeDevToolsUtils", true);
+loader.lazyRequireGetter(this, "ToolboxButtons",
+  "devtools/client/definitions", true);
 
 loader.lazyGetter(this, "registerHarOverlay", () => {
   return require("devtools/client/netmonitor/har/toolbox-overlay").register;
 });
 
-// White-list buttons that can be toggled to prevent adding prefs for
-// addons that have manually inserted toolbarbuttons into DOM.
-// (By default, supported target is only local tab)
-const ToolboxButtons = exports.ToolboxButtons = [
-  { id: "command-button-frames",
-    isTargetSupported: target => {
-      return target.activeTab && target.activeTab.traits.frames;
-    }
-  },
-  { id: "command-button-splitconsole",
-    isTargetSupported: target => !target.isAddon },
-  { id: "command-button-responsive" },
-  { id: "command-button-paintflashing" },
-  { id: "command-button-scratchpad" },
-  { id: "command-button-screenshot" },
-  { id: "command-button-rulers" },
-  { id: "command-button-measure" },
-  { id: "command-button-noautohide",
-    isTargetSupported: target => target.chrome },
-];
-
 /**
  * A "Toolbox" is the component that holds all the tools for one specific
  * target. Visually, it's a document that includes the tools tabs and all
  * the iframes where the tool panels will be living in.
  *
  * @param {object} target
  *        The object the toolbox is debugging.
  * @param {string} selectedTool

--- a/devtools/shared/gcli/commands/index.js
+++ b/devtools/shared/gcli/commands/index.js
@@ -77,31 +77,31 @@ exports.devtoolsModules = [
   "devtools/shared/gcli/commands/security",
 ];
 
 /**
  * Register commands from tools with 'command: [ "some/module" ]' definitions.
  * The map/reduce incantation squashes the array of arrays to a single array.
  */
 try {
-  const defaultTools = require("devtools/client/definitions").defaultTools;
+  const { defaultTools } = require("devtools/client/definitions");
   exports.devtoolsToolModules = defaultTools.map(def => def.commands || [])
                                    .reduce((prev, curr) => prev.concat(curr), []);
 } catch(e) {
   // "definitions" is only accessible from Firefox
   exports.devtoolsToolModules = [];
 }
 
 /**
  * Register commands from toolbox buttons with 'command: [ "some/module" ]'
  * definitions.  The map/reduce incantation squashes the array of arrays to a
  * single array.
  */
 try {
-  const { ToolboxButtons } = require("devtools/client/framework/toolbox");
+  const { ToolboxButtons } = require("devtools/client/definitions");
   exports.devtoolsButtonModules = ToolboxButtons.map(def => def.commands || [])
                                      .reduce((prev, curr) => prev.concat(curr), []);
 } catch(e) {
   // "devtools/framework/toolbox" is only accessible from Firefox
   exports.devtoolsButtonModules = [];
 }
 
 /**