--- a/devtools/client/definitions.js
+++ b/devtools/client/definitions.js
@@ -22,17 +22,17 @@ loader.lazyGetter(this, "PerformancePane
 loader.lazyGetter(this, "NetMonitorPanel", () => require("devtools/client/netmonitor/panel").NetMonitorPanel);
 loader.lazyGetter(this, "StoragePanel", () => require("devtools/client/storage/panel").StoragePanel);
 loader.lazyGetter(this, "ScratchpadPanel", () => require("devtools/client/scratchpad/scratchpad-panel").ScratchpadPanel);
 loader.lazyGetter(this, "DomPanel", () => require("devtools/client/dom/dom-panel").DomPanel);
 
 // Other dependencies
 loader.lazyRequireGetter(this, "CommandUtils", "devtools/client/shared/developer-toolbar", true);
 loader.lazyRequireGetter(this, "CommandState", "devtools/shared/gcli/command-state", true);
-loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsivedesign/responsivedesign");
+loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsive.html/manager", true);
 loader.lazyImporter(this, "ScratchpadManager", "resource://devtools/client/scratchpad/scratchpad-manager.jsm");
 
 const {MultiLocalizationHelper} = require("devtools/shared/l10n");
 const L10N = new MultiLocalizationHelper(
   "devtools/client/locales/startup.properties",
   "devtools/shim/locales/key-shortcuts.properties"
 );
 

--- a/devtools/client/framework/devtools-browser.js
+++ b/devtools/client/framework/devtools-browser.js
@@ -20,17 +20,17 @@ const {gDevTools} = require("./devtools"
 // Load target and toolbox lazily as they need gDevTools to be fully initialized
 loader.lazyRequireGetter(this, "TargetFactory", "devtools/client/framework/target", true);
 loader.lazyRequireGetter(this, "Toolbox", "devtools/client/framework/toolbox", true);
 loader.lazyRequireGetter(this, "DebuggerServer", "devtools/server/main", true);
 loader.lazyRequireGetter(this, "DebuggerClient", "devtools/shared/client/main", true);
 loader.lazyRequireGetter(this, "BrowserMenus", "devtools/client/framework/browser-menus");
 loader.lazyRequireGetter(this, "appendStyleSheet", "devtools/client/shared/stylesheet-utils", true);
 loader.lazyRequireGetter(this, "DeveloperToolbar", "devtools/client/shared/developer-toolbar", true);
-loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsivedesign/responsivedesign");
+loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsive.html/manager", true);
 loader.lazyImporter(this, "BrowserToolboxProcess", "resource://devtools/client/framework/ToolboxProcess.jsm");
 loader.lazyImporter(this, "ScratchpadManager", "resource://devtools/client/scratchpad/scratchpad-manager.jsm");
 
 loader.lazyImporter(this, "CustomizableUI", "resource:///modules/CustomizableUI.jsm");
 loader.lazyImporter(this, "CustomizableWidgets", "resource:///modules/CustomizableWidgets.jsm");
 loader.lazyImporter(this, "AppConstants", "resource://gre/modules/AppConstants.jsm");
 
 const {LocalizationHelper} = require("devtools/shared/l10n");

--- a/devtools/client/menus.js
+++ b/devtools/client/menus.js
@@ -26,17 +26,17 @@
  * - checkbox:
  *   If true, the menuitem is prefixed by a checkbox and runtime code can
  *   toggle it.
  */
 
 loader.lazyRequireGetter(this, "gDevToolsBrowser", "devtools/client/framework/devtools-browser", true);
 loader.lazyRequireGetter(this, "CommandUtils", "devtools/client/shared/developer-toolbar", true);
 loader.lazyRequireGetter(this, "TargetFactory", "devtools/client/framework/target", true);
-loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsivedesign/responsivedesign");
+loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsive.html/manager", true);
 
 loader.lazyImporter(this, "BrowserToolboxProcess", "resource://devtools/client/framework/ToolboxProcess.jsm");
 loader.lazyImporter(this, "ScratchpadManager", "resource://devtools/client/scratchpad/scratchpad-manager.jsm");
 
 exports.menuitems = [
   { id: "menu_devToolbox",
     l10nKey: "devToolboxMenuItem",
     oncommand(event) {

--- a/devtools/client/preferences/devtools.js
+++ b/devtools/client/preferences/devtools.js
@@ -332,11 +332,8 @@ pref("devtools.editor.autoclosebrackets"
 pref("devtools.editor.detectindentation", true);
 pref("devtools.editor.enableCodeFolding", true);
 pref("devtools.editor.autocomplete", true);
 
 // Pref to store the browser version at the time of a telemetry ping for an
 // opened developer tool. This allows us to ping telemetry just once per browser
 // version for each user.
 pref("devtools.telemetry.tools.opened.version", "{}");
-
-// Enable the HTML responsive design mode for all channels.
-pref("devtools.responsive.html.enabled", true);

--- a/devtools/client/responsive.html/manager.js
+++ b/devtools/client/responsive.html/manager.js
@@ -26,20 +26,16 @@ loader.lazyRequireGetter(this, "message"
 loader.lazyRequireGetter(this, "getStr",
   "devtools/client/responsive.html/utils/l10n", true);
 loader.lazyRequireGetter(this, "EmulationFront",
   "devtools/shared/fronts/emulation", true);
 
 /**
  * ResponsiveUIManager is the external API for the browser UI, etc. to use when
  * opening and closing the responsive UI.
- *
- * While the HTML UI is in an experimental stage, the older ResponsiveUIManager
- * from devtools/client/responsivedesign/responsivedesign.jsm delegates to this
- * object when the pref "devtools.responsive.html.enabled" is true.
  */
 const ResponsiveUIManager = exports.ResponsiveUIManager = {
   activeTabs: new Map(),
 
   /**
    * Toggle the responsive UI for a tab.
    *
    * @param window

--- a/devtools/client/responsive.html/test/browser/head.js
+++ b/devtools/client/responsive.html/test/browser/head.js
@@ -46,29 +46,26 @@ SimpleTest.waitForExplicitFinish();
 // on debug builds. Usually we are just barely over the limit, so a blanket factor of 2
 // should be enough.
 requestLongerTimeout(2);
 
 flags.testing = true;
 Services.prefs.clearUserPref("devtools.responsive.html.displayedDeviceList");
 Services.prefs.setCharPref("devtools.devices.url",
   TEST_URI_ROOT + "devices.json");
-Services.prefs.setBoolPref("devtools.responsive.html.enabled", true);
 
 registerCleanupFunction(() => {
   flags.testing = false;
   Services.prefs.clearUserPref("devtools.devices.url");
-  Services.prefs.clearUserPref("devtools.responsive.html.enabled");
   Services.prefs.clearUserPref("devtools.responsive.html.displayedDeviceList");
   asyncStorage.removeItem("devtools.devices.url_cache");
   asyncStorage.removeItem("devtools.devices.local");
 });
 
-// This depends on the "devtools.responsive.html.enabled" pref
-loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsivedesign/responsivedesign");
+loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsive.html/manager", true);
 
 /**
  * Open responsive design mode for the given tab.
  */
 var openRDM = Task.async(function* (tab) {
   info("Opening responsive design mode");
   let manager = ResponsiveUIManager;
   let ui = yield manager.openIfNeeded(tab.ownerGlobal, tab);

--- a/devtools/client/responsivedesign/moz.build
+++ b/devtools/client/responsivedesign/moz.build
@@ -2,13 +2,12 @@
 # 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/.
 
 BROWSER_CHROME_MANIFESTS += ['test/browser.ini']
 
 DevToolsModules(
     'resize-commands.js',
     'responsivedesign-old.js',
-    'responsivedesign.js',
 )
 
 with Files('**'):
     BUG_COMPONENT = ('Firefox', 'Developer Tools: Responsive Design Mode')

--- a/devtools/client/responsivedesign/resize-commands.js
+++ b/devtools/client/responsivedesign/resize-commands.js
@@ -1,17 +1,17 @@
 /* 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/. */
 
 "use strict";
 
 const { Cc, Ci, Cu } = require("chrome");
 
-loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsivedesign/responsivedesign");
+loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsive.html/manager", true);
 
 const BRAND_SHORT_NAME = Cc["@mozilla.org/intl/stringbundle;1"].
                          getService(Ci.nsIStringBundleService).
                          createBundle("chrome://branding/locale/brand.properties").
                          GetStringFromName("brandShortName");
 
 const Services = require("Services");
 const osString = Services.appinfo.OS;

deleted file mode 100644
--- a/devtools/client/responsivedesign/responsivedesign.js
+++ /dev/null
@@ -1,22 +0,0 @@
-/* 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/. */
-
-"use strict";
-
-const Services = require("Services");
-
-const NEW_RDM_ENABLED = "devtools.responsive.html.enabled";
-
-// If the new HTML RDM UI is enabled and e10s is enabled by default (e10s is required for
-// the new HTML RDM UI to function), delegate the ResponsiveUIManager API over to that
-// tool instead.  Performing this delegation here allows us to contain the pref check to a
-// single place.
-if (Services.prefs.getBoolPref(NEW_RDM_ENABLED) &&
-    Services.appinfo.browserTabsRemoteAutostart) {
-  let { ResponsiveUIManager } = require("devtools/client/responsive.html/manager");
-  module.exports = ResponsiveUIManager;
-} else {
-  let { ResponsiveUIManager } = require("devtools/client/responsivedesign/responsivedesign-old");
-  module.exports = ResponsiveUIManager;
-}

--- a/devtools/client/responsivedesign/test/head.js
+++ b/devtools/client/responsivedesign/test/head.js
@@ -22,17 +22,17 @@ registerCleanupFunction(() => {
   Services.prefs.clearUserPref("devtools.responsiveUI.customHeight");
   Services.prefs.clearUserPref("devtools.responsiveUI.customWidth");
   Services.prefs.clearUserPref("devtools.responsiveUI.presets");
   Services.prefs.clearUserPref("devtools.responsiveUI.rotate");
 });
 
 SimpleTest.requestCompleteLog();
 
-loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsivedesign/responsivedesign");
+loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsive.html/manager");
 
 /**
  * Open the Responsive Design Mode
  * @param {Tab} The browser tab to open it into (defaults to the selected tab).
  * @param {method} The method to use to open the RDM (values: menu, keyboard)
  * @return {rdm, manager} Returns the RUI instance and the manager
  */
 var openRDM = Task.async(function* (tab = gBrowser.selectedTab,

--- a/devtools/client/shared/test/browser_telemetry_button_responsive.js
+++ b/devtools/client/shared/test/browser_telemetry_button_responsive.js
@@ -5,17 +5,17 @@
 
 const TEST_URI = "data:text/html;charset=utf-8," +
   "<p>browser_telemetry_button_responsive.js</p>";
 
 // Because we need to gather stats for the period of time that a tool has been
 // opened we make use of setTimeout() to create tool active times.
 const TOOL_DELAY = 200;
 
-loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsivedesign/responsivedesign");
+loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsive.html/manager", true);
 
 add_task(function* () {
   yield addTab(TEST_URI);
   let Telemetry = loadTelemetryAndRecordLogs();
 
   let target = TargetFactory.forTab(gBrowser.selectedTab);
   let toolbox = yield gDevTools.showToolbox(target, "inspector");
   info("inspector opened");

--- a/devtools/client/styleeditor/StyleEditorUI.jsm
+++ b/devtools/client/styleeditor/StyleEditorUI.jsm
@@ -26,17 +26,17 @@ const {
 const {SplitView} = require("resource://devtools/client/shared/SplitView.jsm");
 const {StyleSheetEditor} = require("resource://devtools/client/styleeditor/StyleSheetEditor.jsm");
 const {PluralForm} = require("devtools/shared/plural-form");
 const {PrefObserver} = require("devtools/client/shared/prefs");
 const csscoverage = require("devtools/shared/fronts/csscoverage");
 const {console} = require("resource://gre/modules/Console.jsm");
 const {KeyCodes} = require("devtools/client/shared/keycodes");
 
-loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsivedesign/responsivedesign");
+loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsive.html/manager", true);
 
 const LOAD_ERROR = "error-load";
 const STYLE_EDITOR_TEMPLATE = "stylesheet";
 const SELECTOR_HIGHLIGHTER_TYPE = "SelectorHighlighter";
 const PREF_MEDIA_SIDEBAR = "devtools.styleeditor.showMediaSidebar";
 const PREF_SIDEBAR_WIDTH = "devtools.styleeditor.mediaSidebarWidth";
 const PREF_NAV_WIDTH = "devtools.styleeditor.navSidebarWidth";
 const PREF_ORIG_SOURCES = "devtools.source-map.client-service.enabled";

--- a/devtools/client/styleeditor/test/browser_styleeditor_media_sidebar_links.js
+++ b/devtools/client/styleeditor/test/browser_styleeditor_media_sidebar_links.js
@@ -11,17 +11,17 @@ const asyncStorage = require("devtools/s
 Services.prefs.setCharPref("devtools.devices.url",
   "http://example.com/browser/devtools/client/responsive.html/test/browser/devices.json");
 
 registerCleanupFunction(() => {
   Services.prefs.clearUserPref("devtools.devices.url");
   asyncStorage.removeItem("devtools.devices.url_cache");
 });
 
-loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsivedesign/responsivedesign");
+loader.lazyRequireGetter(this, "ResponsiveUIManager", "devtools/client/responsive.html/manager", true);
 
 const TESTCASE_URI = TEST_BASE_HTTPS + "media-rules.html";
 const responsiveModeToggleClass = ".media-responsive-mode-toggle";
 
 add_task(function* () {
   let {ui} = yield openStyleEditorForURL(TESTCASE_URI);
 
   let editor = ui.editors[1];