--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -1281,18 +1281,17 @@ pref("browser.newtabpage.thumbnailPlaceh
 pref("browser.newtabpage.rows", 3);
 
 // number of columns of newtab grid
 pref("browser.newtabpage.columns", 5);
 
 // directory tiles download URL
 pref("browser.newtabpage.directory.source", "https://tiles.services.mozilla.com/v3/links/fetch/%LOCALE%/%CHANNEL%");
 
-// activates Activity Stream
-pref("browser.newtabpage.activity-stream.enabled", true);
+// Activity Stream prefs that control to which page to redirect
 pref("browser.newtabpage.activity-stream.prerender", true);
 #ifndef RELEASE_OR_BETA
 pref("browser.newtabpage.activity-stream.debug", false);
 #endif
 
 pref("browser.library.activity-stream.enabled", true);
 
 // Enable the DOM fullscreen API.

--- a/browser/base/content/browser-thumbnails.js
+++ b/browser/base/content/browser-thumbnails.js
@@ -9,23 +9,16 @@
  * Keeps thumbnails of open web pages up-to-date.
  */
 var gBrowserThumbnails = {
   /**
    * Pref that controls whether we can store SSL content on disk
    */
   PREF_DISK_CACHE_SSL: "browser.cache.disk_cache_ssl",
 
-  /**
-   * Pref that controls whether activity stream is enabled
-   */
-  PREF_ACTIVITY_STREAM_ENABLED: "browser.newtabpage.activity-stream.enabled",
-
-  _activityStreamEnabled: null,
-
   _captureDelayMS: 1000,
 
   /**
    * Used to keep track of disk_cache_ssl preference
    */
   _sslDiskCacheEnabled: null,
 
   /**
@@ -41,34 +34,30 @@ var gBrowserThumbnails = {
   /**
    * List of tab events we want to listen for.
    */
   _tabEvents: ["TabClose", "TabSelect"],
 
   init: function Thumbnails_init() {
     gBrowser.addTabsProgressListener(this);
     Services.prefs.addObserver(this.PREF_DISK_CACHE_SSL, this);
-    Services.prefs.addObserver(this.PREF_ACTIVITY_STREAM_ENABLED, this);
 
     this._sslDiskCacheEnabled =
       Services.prefs.getBoolPref(this.PREF_DISK_CACHE_SSL);
-    this._activityStreamEnabled =
-      Services.prefs.getBoolPref(this.PREF_ACTIVITY_STREAM_ENABLED);
 
     this._tabEvents.forEach(function(aEvent) {
       gBrowser.tabContainer.addEventListener(aEvent, this);
     }, this);
 
     this._timeouts = new WeakMap();
   },
 
   uninit: function Thumbnails_uninit() {
     gBrowser.removeTabsProgressListener(this);
     Services.prefs.removeObserver(this.PREF_DISK_CACHE_SSL, this);
-    Services.prefs.removeObserver(this.PREF_ACTIVITY_STREAM_ENABLED, this);
 
     if (this._topSiteURLsRefreshTimer) {
       this._topSiteURLsRefreshTimer.cancel();
       this._topSiteURLsRefreshTimer = null;
     }
 
     this._tabEvents.forEach(function(aEvent) {
       gBrowser.tabContainer.removeEventListener(aEvent, this);
@@ -93,22 +82,16 @@ var gBrowserThumbnails = {
   },
 
   observe: function Thumbnails_observe(subject, topic, data) {
     switch (data) {
       case this.PREF_DISK_CACHE_SSL:
         this._sslDiskCacheEnabled =
           Services.prefs.getBoolPref(this.PREF_DISK_CACHE_SSL);
         break;
-      case this.PREF_ACTIVITY_STREAM_ENABLED:
-        this._activityStreamEnabled =
-          Services.prefs.getBoolPref(this.PREF_ACTIVITY_STREAM_ENABLED);
-        // Get the new top sites
-        this.clearTopSiteURLCache();
-        break;
     }
   },
 
   clearTopSiteURLCache: function Thumbnails_clearTopSiteURLCache() {
     if (this._topSiteURLsRefreshTimer) {
       this._topSiteURLsRefreshTimer.cancel();
       this._topSiteURLsRefreshTimer = null;
     }
@@ -204,25 +187,21 @@ async function getTopSiteURLs() {
   // change frequently on new profiles, so as a compromise we cache its return
   // value as a lazy getter for 1 minute every time it's called.
   gBrowserThumbnails._topSiteURLsRefreshTimer =
     Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
   gBrowserThumbnails._topSiteURLsRefreshTimer.initWithCallback(gBrowserThumbnails,
                                                                60 * 1000,
                                                                Ci.nsITimer.TYPE_ONE_SHOT);
   let sites = [];
-  if (gBrowserThumbnails._activityStreamEnabled) {
-    // Get both the top sites returned by the query, and also any pinned sites
-    // that the user might have added manually that also need a screenshot.
-    // Also include top sites that don't have rich icons
-    let topSites = await NewTabUtils.activityStreamLinks.getTopSites();
-    sites.push(...topSites.filter(link => !(link.faviconSize >= 96)));
-    sites.push(...NewTabUtils.pinnedLinks.links);
-  } else {
-    sites = NewTabUtils.links.getLinks();
-  }
+  // Get both the top sites returned by the query, and also any pinned sites
+  // that the user might have added manually that also need a screenshot.
+  // Also include top sites that don't have rich icons
+  let topSites = await NewTabUtils.activityStreamLinks.getTopSites();
+  sites.push(...topSites.filter(link => !(link.faviconSize >= 96)));
+  sites.push(...NewTabUtils.pinnedLinks.links);
   return sites.reduce((urls, link) => {
     if (link) urls.push(link.url);
     return urls;
   }, []);
 }
 
 XPCOMUtils.defineLazyGetter(gBrowserThumbnails, "_topSiteURLs", getTopSiteURLs);

--- a/browser/base/content/test/general/browser_bug724239.js
+++ b/browser/base/content/test/general/browser_bug724239.js
@@ -6,31 +6,19 @@ add_task(async function test_blank() {
                                     async function(browser) {
     BrowserTestUtils.loadURI(browser, "http://example.com");
     await BrowserTestUtils.browserLoaded(browser);
     ok(!gBrowser.canGoBack, "about:blank wasn't added to session history");
   });
 });
 
 add_task(async function test_newtab() {
-  await SpecialPowers.pushPrefEnv({set: [["browser.newtabpage.activity-stream.enabled", true]]});
   await BrowserTestUtils.withNewTab({ gBrowser, url: "about:blank" },
                                     async function(browser) {
     // Can't load it directly because that'll use a preloaded tab if present.
     BrowserTestUtils.loadURI(browser, "about:newtab");
     await BrowserTestUtils.browserLoaded(browser);
 
     BrowserTestUtils.loadURI(browser, "http://example.com");
     await BrowserTestUtils.browserLoaded(browser);
     is(gBrowser.canGoBack, true, "about:newtab was added to the session history when AS was enabled.");
   });
-  await SpecialPowers.pushPrefEnv({set: [["browser.newtabpage.activity-stream.enabled", false]]});
-  await BrowserTestUtils.withNewTab({ gBrowser, url: "about:blank" },
-                                    async function(browser) {
-    // Can't load it directly because that'll use a preloaded tab if present.
-    BrowserTestUtils.loadURI(browser, "about:newtab");
-    await BrowserTestUtils.browserLoaded(browser);
-
-    BrowserTestUtils.loadURI(browser, "http://example.com");
-    await BrowserTestUtils.browserLoaded(browser);
-    is(gBrowser.canGoBack, false, "about:newtab was not added to the session history when AS was disabled.");
-  });
 });

--- a/browser/base/content/test/general/browser_testOpenNewRemoteTabsFromNonRemoteBrowsers.js
+++ b/browser/base/content/test/general/browser_testOpenNewRemoteTabsFromNonRemoteBrowsers.js
@@ -6,17 +6,17 @@ const OPEN_LOCATION_PREF = "browser.link
 const NON_REMOTE_PAGE = "about:welcomeback";
 
 ChromeUtils.import("resource://gre/modules/PrivateBrowsingUtils.jsm");
 
 requestLongerTimeout(2);
 
 function frame_script() {
   content.document.body.innerHTML = `
-    <a href="about:home" target="_blank" id="testAnchor">Open a window</a>
+    <a href="http://example.com/" target="_blank" id="testAnchor">Open a window</a>
   `;
 
   let element = content.document.getElementById("testAnchor");
   element.click();
 }
 
 /**
  * Takes some browser in some window, and forces that browser
@@ -57,17 +57,17 @@ add_task(async function test_new_tab() {
     let mm = testBrowser.messageManager;
     mm.loadFrameScript("data:,(" + frame_script.toString() + ")();", true);
 
     let tabOpenEvent = await waitForNewTabEvent(testWindow.gBrowser);
     let newTab = tabOpenEvent.target;
 
     await promiseTabLoadEvent(newTab);
 
-    // Our framescript opens to about:home which means that the
+    // Our framescript opens to a web page which means that the
     // tab should eventually become remote.
     ok(newTab.linkedBrowser.isRemoteBrowser,
        "The opened browser never became remote.");
 
     testWindow.gBrowser.removeTab(newTab);
   }
 
   normalWindow.close();
@@ -109,17 +109,17 @@ add_task(async function test_new_window(
     is(PrivateBrowsingUtils.isWindowPrivate(testWindow),
        PrivateBrowsingUtils.isWindowPrivate(newWindow),
        "Private browsing state of new window does not match the original!");
 
     let newTab = newWindow.gBrowser.selectedTab;
 
     await promiseTabLoadEvent(newTab);
 
-    // Our framescript opens to about:home which means that the
+    // Our framescript opens to a web page which means that the
     // tab should eventually become remote.
     ok(newTab.linkedBrowser.isRemoteBrowser,
        "The opened browser never became remote.");
     newWindow.close();
   }
 
   normalWindow.close();
   privateWindow.close();

--- a/browser/base/content/test/newtab/browser.ini
+++ b/browser/base/content/test/newtab/browser.ini
@@ -1,10 +1,10 @@
 [DEFAULT]
-skip-if = (os == 'linux') # Bug 1243103, Bug 1243398, etc.
+skip-if = true # Bug 1433133 to remove; previously skipped for intermittents, e.g., Bug 1243103, Bug 1243398
 support-files =
   head.js
 
 [browser_newtab_1188015.js]
 [browser_newtab_background_captures.js]
 [browser_newtab_block.js]
 [browser_newtab_bug721442.js]
 [browser_newtab_bug722273.js]

--- a/browser/base/content/test/newtab/head.js
+++ b/browser/base/content/test/newtab/head.js
@@ -1,17 +1,15 @@
 /* Any copyright is dedicated to the Public Domain.
    http://creativecommons.org/publicdomain/zero/1.0/ */
 
 const PREF_NEWTAB_ENABLED = "browser.newtabpage.enabled";
 const PREF_NEWTAB_DIRECTORYSOURCE = "browser.newtabpage.directory.source";
-const PREF_NEWTAB_ACTIVITY_STREAM = "browser.newtabpage.activity-stream.enabled";
 
 Services.prefs.setBoolPref(PREF_NEWTAB_ENABLED, true);
-Services.prefs.setBoolPref(PREF_NEWTAB_ACTIVITY_STREAM, false);
 
 // Opens and closes a new tab to clear any existing preloaded ones. This is
 // necessary to prevent any left-over activity-stream preloaded new tabs from
 // affecting these tests.
 BrowserOpenTab();
 const initialTab = gBrowser.selectedTab;
 gBrowser.removeTab(initialTab);
 
@@ -91,17 +89,16 @@ add_task(async function setupWindowSize(
         }
       });
     });
   });
 });
 
 registerCleanupFunction(function() {
   Services.prefs.clearUserPref(PREF_NEWTAB_ENABLED);
-  Services.prefs.clearUserPref(PREF_NEWTAB_ACTIVITY_STREAM);
   Services.prefs.setCharPref(PREF_NEWTAB_DIRECTORYSOURCE, gOrigDirectorySource);
 
   return watchLinksChangeOnce();
 });
 
 function pushPrefs(...aPrefs) {
   return SpecialPowers.pushPrefEnv({"set": aPrefs});
 }

--- a/browser/components/about/AboutRedirector.cpp
+++ b/browser/components/about/AboutRedirector.cpp
@@ -16,18 +16,16 @@
 #include "mozilla/Preferences.h"
 #include "nsServiceManagerUtils.h"
 
 namespace mozilla {
 namespace browser {
 
 NS_IMPL_ISUPPORTS(AboutRedirector, nsIAboutModule)
 
-bool AboutRedirector::sActivityStreamEnabled = false;
-
 struct RedirEntry {
   const char* id;
   const char* url;
   uint32_t flags;
 };
 
 /*
   Entries which do not have URI_SAFE_FOR_UNTRUSTED_CONTENT will run with chrome
@@ -71,25 +69,28 @@ static const RedirEntry kRedirMap[] = {
     nsIAboutModule::ALLOW_SCRIPT |
     nsIAboutModule::HIDE_FROM_ABOUTABOUT },
   { "sessionrestore", "chrome://browser/content/aboutSessionRestore.xhtml",
     nsIAboutModule::ALLOW_SCRIPT |
     nsIAboutModule::HIDE_FROM_ABOUTABOUT },
   { "welcomeback", "chrome://browser/content/aboutWelcomeBack.xhtml",
     nsIAboutModule::ALLOW_SCRIPT |
     nsIAboutModule::HIDE_FROM_ABOUTABOUT },
+  // Actual activity stream URL for home and newtab are set in channel creation
   // Linkable because of indexeddb use (bug 1228118)
-  { "home", "chrome://browser/content/abouthome/aboutHome.xhtml",
+  { "home", "about:blank",
     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
     nsIAboutModule::URI_MUST_LOAD_IN_CHILD |
     nsIAboutModule::ALLOW_SCRIPT |
     nsIAboutModule::MAKE_LINKABLE |
     nsIAboutModule::ENABLE_INDEXED_DB },
-  // the newtab's actual URL will be determined when the channel is created
   { "newtab", "about:blank",
+    nsIAboutModule::ENABLE_INDEXED_DB |
+    nsIAboutModule::URI_MUST_LOAD_IN_CHILD |
+    nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
     nsIAboutModule::ALLOW_SCRIPT },
   { "preferences", "chrome://browser/content/preferences/in-content/preferences.xul",
     nsIAboutModule::ALLOW_SCRIPT },
   { "downloads", "chrome://browser/content/downloads/contentAreaDownloadsView.xul",
     nsIAboutModule::ALLOW_SCRIPT },
   { "reader", "chrome://global/content/reader/aboutReader.html",
     nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
     nsIAboutModule::ALLOW_SCRIPT |
@@ -110,51 +111,37 @@ GetAboutModuleName(nsIURI *aURI)
   f = path.FindChar('?');
   if (f >= 0)
     path.SetLength(f);
 
   ToLowerCase(path);
   return path;
 }
 
-void
-AboutRedirector::LoadActivityStreamPrefs()
-{
-  static bool sASEnabledCacheInited = false;
-  if (!sASEnabledCacheInited) {
-    Preferences::AddBoolVarCache(&AboutRedirector::sActivityStreamEnabled,
-                                 "browser.newtabpage.activity-stream.enabled");
-    sASEnabledCacheInited = true;
-  }
-}
-
 NS_IMETHODIMP
 AboutRedirector::NewChannel(nsIURI* aURI,
                             nsILoadInfo* aLoadInfo,
                             nsIChannel** result)
 {
   NS_ENSURE_ARG_POINTER(aURI);
   NS_ENSURE_ARG_POINTER(aLoadInfo);
 
   NS_ASSERTION(result, "must not be null");
 
   nsAutoCString path = GetAboutModuleName(aURI);
 
   nsresult rv;
   nsCOMPtr<nsIIOService> ioService = do_GetIOService(&rv);
   NS_ENSURE_SUCCESS(rv, rv);
 
-  LoadActivityStreamPrefs();
-
   for (auto & redir : kRedirMap) {
     if (!strcmp(path.get(), redir.id)) {
       nsAutoCString url;
 
-      if (path.EqualsLiteral("newtab") ||
-          (path.EqualsLiteral("home") && sActivityStreamEnabled)) {
+      if (path.EqualsLiteral("newtab") || path.EqualsLiteral("home")) {
         // let the aboutNewTabService decide where to redirect
         nsCOMPtr<nsIAboutNewTabService> aboutNewTabService =
           do_GetService("@mozilla.org/browser/aboutnewtab-service;1", &rv);
         NS_ENSURE_SUCCESS(rv, rv);
         rv = aboutNewTabService->GetDefaultURL(url);
         NS_ENSURE_SUCCESS(rv, rv);
       }
       // fall back to the specified url in the map
@@ -196,34 +183,18 @@ AboutRedirector::NewChannel(nsIURI* aURI
 
 NS_IMETHODIMP
 AboutRedirector::GetURIFlags(nsIURI *aURI, uint32_t *result)
 {
   NS_ENSURE_ARG_POINTER(aURI);
 
   nsAutoCString name = GetAboutModuleName(aURI);
 
-  LoadActivityStreamPrefs();
-
   for (auto & redir : kRedirMap) {
     if (name.Equals(redir.id)) {
-
-      // Once ActivityStream is fully rolled out and we've removed Tiles,
-      // this special case can go away and the flag can just become part
-      // of the normal about:newtab entry in kRedirMap.
-      if (name.EqualsLiteral("newtab") || name.EqualsLiteral("home")) {
-        if (sActivityStreamEnabled) {
-          *result = redir.flags |
-            nsIAboutModule::URI_MUST_LOAD_IN_CHILD |
-            nsIAboutModule::ENABLE_INDEXED_DB |
-            nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT;
-          return NS_OK;
-        }
-      }
-
       *result = redir.flags;
       return NS_OK;
     }
   }
 
   return NS_ERROR_ILLEGAL_VALUE;
 }
 

--- a/browser/components/about/AboutRedirector.h
+++ b/browser/components/about/AboutRedirector.h
@@ -19,19 +19,14 @@ public:
 
   AboutRedirector() {}
 
   static nsresult
     Create(nsISupports *aOuter, REFNSIID aIID, void **aResult);
 
 protected:
   virtual ~AboutRedirector() {}
-
-private:
-  static bool sActivityStreamEnabled;
-
-  static void LoadActivityStreamPrefs();
 };
 
 } // namespace browser
 } // namespace mozilla
 
 #endif // AboutRedirector_h__

--- a/browser/components/about/test/unit/test_getURIFlags.js
+++ b/browser/components/about/test/unit/test_getURIFlags.js
@@ -1,31 +1,16 @@
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 const contract = "@mozilla.org/network/protocol/about;1?what=newtab";
 const am = Cc[contract].getService(Ci.nsIAboutModule);
 const uri = Services.io.newURI("about:newtab");
 
 function run_test() {
   test_AS_enabled_flags();
-  test_AS_disabled_flags();
-}
-
-// Since tiles isn't e10s capable, it shouldn't advertise that it can load in
-// the child.
-function test_AS_disabled_flags() {
-  Services.prefs.setBoolPref("browser.newtabpage.activity-stream.enabled",
-    false);
-
-  let flags = am.getURIFlags(uri);
-
-  ok(!(flags & Ci.nsIAboutModule.URI_MUST_LOAD_IN_CHILD));
 }
 
 // Activity Stream, however, is e10s-capable, and should advertise it.
 function test_AS_enabled_flags() {
-  Services.prefs.setBoolPref("browser.newtabpage.activity-stream.enabled",
-    true);
-
   let flags = am.getURIFlags(uri);
 
   ok(flags & Ci.nsIAboutModule.URI_MUST_LOAD_IN_CHILD);
 }

--- a/browser/components/newtab/NewTabPrefsProvider.jsm
+++ b/browser/components/newtab/NewTabPrefsProvider.jsm
@@ -7,17 +7,16 @@ ChromeUtils.import("resource://gre/modul
 
 XPCOMUtils.defineLazyGetter(this, "EventEmitter", function() {
   const {EventEmitter} = ChromeUtils.import("resource://gre/modules/EventEmitter.jsm", {});
   return EventEmitter;
 });
 
 // Supported prefs and data type
 const gPrefsMap = new Map([
-  ["browser.newtabpage.activity-stream.enabled", "bool"],
   ["browser.newtabpage.enabled", "bool"],
   ["browser.newtabpage.enhanced", "bool"],
   ["browser.newtabpage.introShown", "bool"],
   ["browser.newtabpage.updateIntroShown", "bool"],
   ["browser.newtabpage.pinned", "str"],
   ["browser.newtabpage.blocked", "str"],
   ["browser.search.hiddenOneOffs", "str"],
 ]);

--- a/browser/components/newtab/aboutNewTabService.js
+++ b/browser/components/newtab/aboutNewTabService.js
@@ -8,76 +8,73 @@
 
 ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 ChromeUtils.import("resource://gre/modules/AppConstants.jsm");
 
 ChromeUtils.defineModuleGetter(this, "AboutNewTab",
                                "resource:///modules/AboutNewTab.jsm");
 
-const LOCAL_NEWTAB_URL = "chrome://browser/content/newtab/newTab.xhtml";
+// Dummy references to the files that this service no longer allows loading.
+// Bug 1409054 to remove "chrome://browser/content/abouthome/aboutHome.xhtml"
+// Bug 1433133 to remove "chrome://browser/content/newtab/newTab.xhtml"
+
 const TOPIC_APP_QUIT = "quit-application-granted";
 const TOPIC_LOCALES_CHANGE = "intl:requested-locales-changed";
 
 // Automated tests ensure packaged locales are in this list. Copied output of:
 // https://github.com/mozilla/activity-stream/blob/master/bin/render-activity-stream-html.js
 const ACTIVITY_STREAM_LOCALES = "en-US ach ar ast az be bg bn-BD bn-IN br bs ca cak cs cy da de dsb el en-GB eo es-AR es-CL es-ES es-MX et eu fa ff fi fr fy-NL ga-IE gd gl gn gu-IN he hi-IN hr hsb hu hy-AM ia id it ja ka kab kk km kn ko lij lo lt ltg lv mk ml mr ms my nb-NO ne-NP nl nn-NO pa-IN pl pt-BR pt-PT rm ro ru si sk sl sq sr sv-SE ta te th tl tr uk ur uz vi zh-CN zh-TW".split(" ");
 
 const ABOUT_URL = "about:newtab";
 
 const IS_MAIN_PROCESS = Services.appinfo.processType === Services.appinfo.PROCESS_TYPE_DEFAULT;
 
 const IS_RELEASE_OR_BETA = AppConstants.RELEASE_OR_BETA;
 
-// Pref that tells if activity stream is enabled
-const PREF_ACTIVITY_STREAM_ENABLED = "browser.newtabpage.activity-stream.enabled";
 const PREF_ACTIVITY_STREAM_PRERENDER_ENABLED = "browser.newtabpage.activity-stream.prerender";
 const PREF_ACTIVITY_STREAM_DEBUG = "browser.newtabpage.activity-stream.debug";
 
 
 function AboutNewTabService() {
   Services.obs.addObserver(this, TOPIC_APP_QUIT);
   Services.obs.addObserver(this, TOPIC_LOCALES_CHANGE);
-  Services.prefs.addObserver(PREF_ACTIVITY_STREAM_ENABLED, this);
   Services.prefs.addObserver(PREF_ACTIVITY_STREAM_PRERENDER_ENABLED, this);
   if (!IS_RELEASE_OR_BETA) {
     Services.prefs.addObserver(PREF_ACTIVITY_STREAM_DEBUG, this);
   }
 
   // More initialization happens here
-  this.toggleActivityStream();
+  this.toggleActivityStream(true);
   this.initialized = true;
 
   if (IS_MAIN_PROCESS) {
     AboutNewTab.init();
   }
 }
 
 /*
  * A service that allows for the overriding, at runtime, of the newtab page's url.
- * Additionally, the service manages pref state between a activity stream, or the regular
- * about:newtab page.
  *
  * There is tight coupling with browser/about/AboutRedirector.cpp.
  *
  * 1. Browser chrome access:
  *
  * When the user issues a command to open a new tab page, usually clicking a button
  * in the browser chrome or using shortcut keys, the browser chrome code invokes the
  * service to obtain the newtab URL. It then loads that URL in a new tab.
  *
  * When not overridden, the default URL emitted by the service is "about:newtab".
  * When overridden, it returns the overriden URL.
  *
  * 2. Redirector Access:
  *
  * When the URL loaded is about:newtab, the default behavior, or when entered in the
- * URL bar, the redirector is hit. The service is then called to return either of
- * two URLs, a chrome or the activity stream one, based on the
- * browser.newtabpage.activity-stream.enabled pref.
+ * URL bar, the redirector is hit. The service is then called to return the
+ * appropriate activity stream url based on prefs and locales.
  *
  * NOTE: "about:newtab" will always result in a default newtab page, and never an overridden URL.
  *
  * Access patterns:
  *
  * The behavior is different when accessing the service via browser chrome or via redirector
  * largely to maintain compatibility with expectations of add-on developers.
  *
@@ -102,21 +99,17 @@ AboutNewTabService.prototype = {
   ]),
   _xpcom_categories: [{
     service: true
   }],
 
   observe(subject, topic, data) {
     switch (topic) {
       case "nsPref:changed":
-        if (data === PREF_ACTIVITY_STREAM_ENABLED) {
-          if (this.toggleActivityStream()) {
-            this.notifyChange();
-          }
-        } else if (data === PREF_ACTIVITY_STREAM_PRERENDER_ENABLED) {
+        if (data === PREF_ACTIVITY_STREAM_PRERENDER_ENABLED) {
           this._activityStreamPrerender = Services.prefs.getBoolPref(PREF_ACTIVITY_STREAM_PRERENDER_ENABLED);
           this.notifyChange();
         } else if (!IS_RELEASE_OR_BETA && data === PREF_ACTIVITY_STREAM_DEBUG) {
           this._activityStreamDebug = Services.prefs.getBoolPref(PREF_ACTIVITY_STREAM_DEBUG, false);
           this.updatePrerenderedPath();
           this.notifyChange();
         }
         break;
@@ -133,31 +126,26 @@ AboutNewTabService.prototype = {
     }
   },
 
   notifyChange() {
     Services.obs.notifyObservers(null, "newtab-url-changed", this._newTabURL);
   },
 
   /**
-   * React to changes to the activity stream pref.
-   *
-   * If browser.newtabpage.activity-stream.enabled is true, this will change the default URL to the
-   * activity stream page URL. If browser.newtabpage.activity-stream.enabled is false, the default URL
-   * will be a local chrome URL.
+   * React to changes to the activity stream being enabled or not.
    *
    * This will only act if there is a change of state and if not overridden.
    *
    * @returns {Boolean} Returns if there has been a state change
    *
    * @param {Boolean}   stateEnabled    activity stream enabled state to set to
    * @param {Boolean}   forceState      force state change
    */
-  toggleActivityStream(stateEnabled = Services.prefs.getBoolPref(PREF_ACTIVITY_STREAM_ENABLED),
-                       forceState = false) {
+  toggleActivityStream(stateEnabled, forceState = false) {
 
     if (!forceState && (this.overridden || stateEnabled === this.activityStreamEnabled)) {
       // exit there is no change of state
       return false;
     }
     if (stateEnabled) {
       this._activityStreamEnabled = true;
     } else {
@@ -185,37 +173,32 @@ AboutNewTabService.prototype = {
         // defaultLocale's strings aren't necessarily packaged, but en-US' are
         "en-US"
       )[0]}/`;
   },
 
   /*
    * Returns the default URL.
    *
-   * This URL only depends on the browser.newtabpage.activity-stream.enabled pref. Overriding
+   * This URL depends on various activity stream prefs and locales. Overriding
    * the newtab page has no effect on the result of this function.
-   *
-   * @returns {String} the default newtab URL, activity-stream or regular depending on browser.newtabpage.activity-stream.enabled
    */
   get defaultURL() {
-    if (this.activityStreamEnabled) {
-      // Generate the desired activity stream resource depending on state, e.g.,
-      // resource://activity-stream/prerendered/ar/activity-stream.html
-      // resource://activity-stream/prerendered/en-US/activity-stream-prerendered.html
-      // resource://activity-stream/prerendered/static/activity-stream-debug.html
-      return [
-        "resource://activity-stream/prerendered/",
-        this._activityStreamPath,
-        "activity-stream",
-        this._activityStreamPrerender ? "-prerendered" : "",
-        this._activityStreamDebug ? "-debug" : "",
-        ".html"
-      ].join("");
-    }
-    return LOCAL_NEWTAB_URL;
+    // Generate the desired activity stream resource depending on state, e.g.,
+    // resource://activity-stream/prerendered/ar/activity-stream.html
+    // resource://activity-stream/prerendered/en-US/activity-stream-prerendered.html
+    // resource://activity-stream/prerendered/static/activity-stream-debug.html
+    return [
+      "resource://activity-stream/prerendered/",
+      this._activityStreamPath,
+      "activity-stream",
+      this._activityStreamPrerender ? "-prerendered" : "",
+      this._activityStreamDebug ? "-debug" : "",
+      ".html"
+    ].join("");
   },
 
   get newTabURL() {
     return this._newTabURL;
   },
 
   set newTabURL(aNewTabURL) {
     aNewTabURL = aNewTabURL.trim();
@@ -247,27 +230,26 @@ AboutNewTabService.prototype = {
 
   get activityStreamDebug() {
     return this._activityStreamDebug;
   },
 
   resetNewTabURL() {
     this._overridden = false;
     this._newTabURL = ABOUT_URL;
-    this.toggleActivityStream(undefined, true);
+    this.toggleActivityStream(true, true);
     this.notifyChange();
   },
 
   uninit() {
     if (!this.initialized) {
       return;
     }
     Services.obs.removeObserver(this, TOPIC_APP_QUIT);
     Services.obs.removeObserver(this, TOPIC_LOCALES_CHANGE);
-    Services.prefs.removeObserver(PREF_ACTIVITY_STREAM_ENABLED, this);
     Services.prefs.removeObserver(PREF_ACTIVITY_STREAM_PRERENDER_ENABLED, this);
     if (!IS_RELEASE_OR_BETA) {
       Services.prefs.removeObserver(PREF_ACTIVITY_STREAM_DEBUG, this);
     }
     this.initialized = false;
   }
 };
 

--- a/browser/components/newtab/tests/browser/browser_newtab_overrides.js
+++ b/browser/components/newtab/tests/browser/browser_newtab_overrides.js
@@ -1,22 +1,18 @@
 "use strict";
 
 ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-const PREF_NEWTAB_ACTIVITY_STREAM = "browser.newtabpage.activity-stream.enabled";
-
-Services.prefs.setBoolPref(PREF_NEWTAB_ACTIVITY_STREAM, false);
 
 XPCOMUtils.defineLazyServiceGetter(this, "aboutNewTabService",
                                    "@mozilla.org/browser/aboutnewtab-service;1",
                                    "nsIAboutNewTabService");
 
 registerCleanupFunction(function() {
-  Services.prefs.clearUserPref(PREF_NEWTAB_ACTIVITY_STREAM);
   aboutNewTabService.resetNewTabURL();
 });
 
 /*
  * Tests that the default newtab page is always returned when one types "about:newtab" in the URL bar,
  * even when overridden.
  */
 add_task(async function redirector_ignores_override() {
@@ -43,19 +39,19 @@ add_task(async function redirector_ignor
      * Bug 1240169 - We expect the redirector to lead the user to "about:newtab", the default URL,
      * due to invoking AboutRedirector. A user interacting with the chrome otherwise would lead
      * to the overriding URLs.
      */
     await BrowserTestUtils.withNewTab(tabOptions, async function(browser) {
       await ContentTask.spawn(browser, {}, async function() {
         Assert.equal(content.location.href, "about:newtab", "Got right URL");
         Assert.equal(content.document.location.href, "about:newtab", "Got right URL");
-        Assert.equal(content.document.nodePrincipal,
+        Assert.notEqual(content.document.nodePrincipal,
           Services.scriptSecurityManager.getSystemPrincipal(),
-          "nodePrincipal should match systemPrincipal");
+          "activity stream principal should not match systemPrincipal");
       });
     }); // jshint ignore:line
   }
 });
 
 /*
  * Tests loading an overridden newtab page by simulating opening a newtab page from chrome
  */

--- a/browser/components/newtab/tests/xpcshell/test_AboutNewTabService.js
+++ b/browser/components/newtab/tests/xpcshell/test_AboutNewTabService.js
@@ -14,51 +14,43 @@ XPCOMUtils.defineLazyServiceGetter(this,
 
 const IS_RELEASE_OR_BETA = AppConstants.RELEASE_OR_BETA;
 
 const ACTIVITY_STREAM_PRERENDER_URL = "resource://activity-stream/prerendered/en-US/activity-stream-prerendered.html";
 const ACTIVITY_STREAM_PRERENDER_DEBUG_URL = "resource://activity-stream/prerendered/static/activity-stream-prerendered-debug.html";
 const ACTIVITY_STREAM_URL = "resource://activity-stream/prerendered/en-US/activity-stream.html";
 const ACTIVITY_STREAM_DEBUG_URL = "resource://activity-stream/prerendered/static/activity-stream-debug.html";
 
-const DEFAULT_CHROME_URL = "chrome://browser/content/newtab/newTab.xhtml";
 const DOWNLOADS_URL = "chrome://browser/content/downloads/contentAreaDownloadsView.xul";
-const ACTIVITY_STREAM_PREF = "browser.newtabpage.activity-stream.enabled";
 const ACTIVITY_STREAM_PRERENDER_PREF = "browser.newtabpage.activity-stream.prerender";
 const ACTIVITY_STREAM_DEBUG_PREF = "browser.newtabpage.activity-stream.debug";
 
 function cleanup() {
-  Services.prefs.clearUserPref(ACTIVITY_STREAM_PREF);
   Services.prefs.clearUserPref(ACTIVITY_STREAM_PRERENDER_PREF);
   Services.prefs.clearUserPref(ACTIVITY_STREAM_DEBUG_PREF);
   aboutNewTabService.resetNewTabURL();
 }
 
 registerCleanupFunction(cleanup);
 
 add_task(async function test_as_and_prerender_initialized() {
-  Assert.equal(aboutNewTabService.activityStreamEnabled, Services.prefs.getBoolPref(ACTIVITY_STREAM_PREF),
+  Assert.ok(aboutNewTabService.activityStreamEnabled,
     ".activityStreamEnabled should be set to the correct initial value");
   Assert.equal(aboutNewTabService.activityStreamPrerender, Services.prefs.getBoolPref(ACTIVITY_STREAM_PRERENDER_PREF),
     ".activityStreamPrerender should be set to the correct initial value");
   // This pref isn't defined on release or beta, so we fall back to false
   Assert.equal(aboutNewTabService.activityStreamDebug, Services.prefs.getBoolPref(ACTIVITY_STREAM_DEBUG_PREF, false),
     ".activityStreamDebug should be set to the correct initial value");
 });
 
 /**
  * Test the overriding of the default URL
  */
 add_task(async function test_override_activity_stream_disabled() {
   let notificationPromise;
-  Services.prefs.setBoolPref(ACTIVITY_STREAM_PREF, false);
-
-  // tests default is the local newtab resource
-  Assert.equal(aboutNewTabService.defaultURL, DEFAULT_CHROME_URL,
-               `Default newtab URL should be ${DEFAULT_CHROME_URL}`);
 
   // override with some remote URL
   let url = "http://example.com/";
   notificationPromise = nextChangeNotificationPromise(url);
   aboutNewTabService.newTabURL = url;
   await notificationPromise;
   Assert.ok(aboutNewTabService.overridden, "Newtab URL should be overridden");
   Assert.ok(!aboutNewTabService.activityStreamEnabled, "Newtab activity stream should not be enabled");
@@ -84,24 +76,24 @@ add_task(async function test_override_ac
 add_task(async function test_override_activity_stream_enabled() {
   let notificationPromise = await setupASPrerendered();
 
   Assert.equal(aboutNewTabService.defaultURL, ACTIVITY_STREAM_PRERENDER_URL, "Newtab URL should be the default activity stream prerendered URL");
   Assert.ok(!aboutNewTabService.overridden, "Newtab URL should not be overridden");
   Assert.ok(aboutNewTabService.activityStreamEnabled, "Activity Stream should be enabled");
   Assert.ok(aboutNewTabService.activityStreamPrerender, "Activity Stream should be prerendered");
 
-  // change to local newtab page while activity stream is enabled
-  notificationPromise = nextChangeNotificationPromise(DEFAULT_CHROME_URL);
-  aboutNewTabService.newTabURL = DEFAULT_CHROME_URL;
+  // change to a chrome URL while activity stream is enabled
+  notificationPromise = nextChangeNotificationPromise(DOWNLOADS_URL);
+  aboutNewTabService.newTabURL = DOWNLOADS_URL;
   await notificationPromise;
-  Assert.equal(aboutNewTabService.newTabURL, DEFAULT_CHROME_URL,
+  Assert.equal(aboutNewTabService.newTabURL, DOWNLOADS_URL,
                "Newtab URL set to chrome url");
-  Assert.equal(aboutNewTabService.defaultURL, DEFAULT_CHROME_URL,
-               "Newtab URL defaultURL set to the default chrome URL");
+  Assert.equal(aboutNewTabService.defaultURL, ACTIVITY_STREAM_PRERENDER_URL,
+               "Newtab URL defaultURL still set to the default activity stream prerendered URL");
   Assert.ok(aboutNewTabService.overridden, "Newtab URL should be overridden");
   Assert.ok(!aboutNewTabService.activityStreamEnabled, "Activity Stream should not be enabled");
 
   cleanup();
 });
 
 add_task(async function test_default_url() {
   await setupASPrerendered();
@@ -193,20 +185,16 @@ function setBoolPrefAndWaitForChange(pre
     }, "newtab-url-changed");
 
     Services.prefs.setBoolPref(pref, value);
   });
 }
 
 
 function setupASPrerendered() {
-  if (Services.prefs.getBoolPref(ACTIVITY_STREAM_PREF) &&
-    Services.prefs.getBoolPref(ACTIVITY_STREAM_PRERENDER_PREF)) {
+  if (Services.prefs.getBoolPref(ACTIVITY_STREAM_PRERENDER_PREF)) {
     return Promise.resolve();
   }
 
-  let notificationPromise;
-  // change newtab page to activity stream
-  notificationPromise = nextChangeNotificationPromise("about:newtab");
-  Services.prefs.setBoolPref(ACTIVITY_STREAM_PREF, true);
+  let notificationPromise = nextChangeNotificationPromise("about:newtab");
   Services.prefs.setBoolPref(ACTIVITY_STREAM_PRERENDER_PREF, true);
   return notificationPromise;
 }

--- a/browser/components/nsBrowserGlue.js
+++ b/browser/components/nsBrowserGlue.js
@@ -362,23 +362,20 @@ BrowserGlue.prototype = {
   get browserErrorReporter() {
     Object.defineProperty(this, "browserErrorReporter", {
       value: new BrowserErrorReporter(),
     });
     return this.browserErrorReporter;
   },
 
   _sendMainPingCentrePing() {
-    const ACTIVITY_STREAM_ENABLED_PREF = "browser.newtabpage.activity-stream.enabled";
     const ACTIVITY_STREAM_ID = "activity-stream";
-    let asEnabled = Services.prefs.getBoolPref(ACTIVITY_STREAM_ENABLED_PREF, false);
-
     const payload = {
       event: "AS_ENABLED",
-      value: asEnabled
+      value: true
     };
     const options = {filter: ACTIVITY_STREAM_ID};
     this.pingCentre.sendPing(payload, options);
   },
 
   // nsIObserver implementation
   observe: function BG_observe(subject, topic, data) {
     switch (topic) {

--- a/browser/components/originattributes/test/browser/browser_firstPartyIsolation_about_newtab.js
+++ b/browser/components/originattributes/test/browser/browser_firstPartyIsolation_about_newtab.js
@@ -1,19 +1,13 @@
 add_task(async function setup() {
   Services.prefs.setBoolPref("privacy.firstparty.isolate", true);
-  // activity-stream is only enabled in Nightly, and if activity-stream is not
-  // enabled, about:newtab is loaded without the flag
-  // nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT, so it will be loaded with
-  // System Principal.
-  Services.prefs.setBoolPref("browser.newtabpage.activity-stream.enabled", true);
 
   registerCleanupFunction(function() {
     Services.prefs.clearUserPref("privacy.firstparty.isolate");
-    Services.prefs.clearUserPref("browser.newtabpage.activity-stream.enabled");
   });
 });
 
 /**
  * Test about:newtab will have firstPartytDomain set when we enable the pref.
  *
  * We split about:newtab from browser_firstPartyIsolation_aboutPages.js because
  * about:newtab needs special care.

--- a/browser/components/sessionstore/test/browser_background_tab_crash.js
+++ b/browser/components/sessionstore/test/browser_background_tab_crash.js
@@ -222,22 +222,16 @@ add_task(async function test_background_
 
 // Tests that crashed preloaded tabs are removed and no unexpected errors are
 // thrown.
 add_task(async function test_preload_crash() {
   if (!Services.prefs.getBoolPref("browser.newtab.preload")) {
     return;
   }
 
-  // Since new tab is only crashable for the activity-stream version,
-  // we need to flip the pref
-  await SpecialPowers.pushPrefEnv({
-    set: [[ "browser.newtabpage.activity-stream.enabled", true ]]
-  });
-
   // Release any existing preloaded browser
   gBrowser.removePreloadedBrowser();
 
   // Create a fresh preloaded browser
   gBrowser._createPreloadBrowser();
 
   await BrowserTestUtils.crashBrowser(gBrowser._preloadedBrowser, false);
 

--- a/browser/components/tests/unit/test_browserGlue_pingcentre.js
+++ b/browser/components/tests/unit/test_browserGlue_pingcentre.js
@@ -1,25 +1,22 @@
 ChromeUtils.import("resource:///modules/PingCentre.jsm");
 
 const TOPIC_SHIELD_INIT_COMPLETE = "shield-init-complete";
-const ACTIVITY_STREAM_ENABLED_PREF = "browser.newtabpage.activity-stream.enabled";
 const SEND_PING_MOCK = sinon.stub(PingCentre.prototype, "sendPing");
 
 let gBrowserGlue = Cc["@mozilla.org/browser/browserglue;1"]
                      .getService(Ci.nsIObserver);
 
 add_task(async function() {
-  let asEnabled = Services.prefs.getBoolPref(ACTIVITY_STREAM_ENABLED_PREF, false);
-
   // Simulate ping centre sendPing() trigger.
   gBrowserGlue.observe(null, TOPIC_SHIELD_INIT_COMPLETE, null);
 
   const SEND_PING_CALL_ARGS = {
     event: "AS_ENABLED",
-    value: asEnabled
+    value: true
   };
   const SEND_PING_FILTER = { filter: "activity-stream" };
 
   Assert.ok(SEND_PING_MOCK.called, "gBrowserGlue.pingCentre.sendPing() is called");
   Assert.ok(SEND_PING_MOCK.calledWithExactly(SEND_PING_CALL_ARGS, SEND_PING_FILTER),
     "sendPing() is called with the correct param");
 });

--- a/browser/extensions/activity-stream/README.md
+++ b/browser/extensions/activity-stream/README.md
@@ -1,10 +1,9 @@
 # activity-stream
 
 This system add-on replaces the new tab page in Firefox with a new design and
-functionality as part of the Activity Stream project. It can be enabled (or disabled)
-via the browser.newtabpage.activity-stream.enabled pref.
+functionality as part of the Activity Stream project.
 
 The files in this directory, including vendor dependencies, are imported from the
 system-addon directory in https://github.com/mozilla/activity-stream.
 
 Read [docs/v2-system-addon](https://github.com/mozilla/activity-stream/tree/master/docs/v2-system-addon/1.GETTING_STARTED.md) for more detail.

--- a/browser/extensions/activity-stream/bootstrap.js
+++ b/browser/extensions/activity-stream/bootstrap.js
@@ -4,17 +4,16 @@
 "use strict";
 
 ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.importGlobalProperties(["fetch"]);
 
 ChromeUtils.defineModuleGetter(this, "Services",
   "resource://gre/modules/Services.jsm");
 
-const ACTIVITY_STREAM_ENABLED_PREF = "browser.newtabpage.activity-stream.enabled";
 const BROWSER_READY_NOTIFICATION = "sessionstore-windows-restored";
 const PREF_CHANGED_TOPIC = "nsPref:changed";
 const REASON_SHUTDOWN_ON_PREF_CHANGE = "PREF_OFF";
 const REASON_STARTUP_ON_PREF_CHANGE = "PREF_ON";
 const RESOURCE_BASE = "resource://activity-stream";
 
 const ACTIVITY_STREAM_OPTIONS = {newTabURL: "about:newtab"};
 
@@ -42,18 +41,17 @@ XPCOMUtils.defineLazyModuleGetter(this, 
           }
         });
       }
     });
   });
 
 /**
  * init - Initializes an instance of ActivityStream. This could be called by
- *        the startup() function exposed by bootstrap.js, or it could be called
- *        when ACTIVITY_STREAM_ENABLED_PREF is changed from false to true.
+ *        the startup() function exposed by bootstrap.js.
  *
  * @param  {string} reason - Reason for initialization. Could be install, upgrade, or PREF_ON
  */
 function init(reason) {
   // Don't re-initialize
   if (activityStream && activityStream.initialized) {
     return;
   }
@@ -63,42 +61,29 @@ function init(reason) {
     activityStream.init(reason);
   } catch (e) {
     Cu.reportError(e);
   }
 }
 
 /**
  * uninit - Uninitializes the activityStream instance, if it exsits.This could be
- *          called by the shutdown() function exposed by bootstrap.js, or it could
- *          be called when ACTIVITY_STREAM_ENABLED_PREF is changed from true to false.
+ *          called by the shutdown() function exposed by bootstrap.js.
  *
  * @param  {type} reason Reason for uninitialization. Could be uninstall, upgrade, or PREF_OFF
  */
 function uninit(reason) {
   // Make sure to only uninit once in case both pref change and shutdown happen
   if (activityStream) {
     activityStream.uninit(reason);
     activityStream = null;
   }
 }
 
 /**
- * onPrefChanged - handler for changes to ACTIVITY_STREAM_ENABLED_PREF
- *
- */
-function onPrefChanged() {
-  if (Services.prefs.getBoolPref(ACTIVITY_STREAM_ENABLED_PREF, false)) {
-    init(REASON_STARTUP_ON_PREF_CHANGE);
-  } else {
-    uninit(REASON_SHUTDOWN_ON_PREF_CHANGE);
-  }
-}
-
-/**
  * Check if an old pref has a custom value to migrate. Clears the pref so that
  * it's the default after migrating (to avoid future need to migrate).
  *
  * @param oldPrefName {string} Pref to check and migrate
  * @param cbIfNotDefault {function} Callback that gets the current pref value
  */
 function migratePref(oldPrefName, cbIfNotDefault) {
   // Nothing to do if the user doesn't have a custom value
@@ -125,24 +110,17 @@ function migratePref(oldPrefName, cbIfNo
   Services.prefs.clearUserPref(oldPrefName);
 }
 
 /**
  * onBrowserReady - Continues startup of the add-on after browser is ready.
  */
 function onBrowserReady() {
   waitingForBrowserReady = false;
-
-  // Listen for changes to the pref that enables Activity Stream
-  Services.prefs.addObserver(ACTIVITY_STREAM_ENABLED_PREF, observe); // eslint-disable-line no-use-before-define
-
-  // Only initialize if the pref is true
-  if (Services.prefs.getBoolPref(ACTIVITY_STREAM_ENABLED_PREF, false)) {
-    init(startupReason);
-  }
+  init(startupReason);
 
   // Do a one time migration of Tiles about:newtab prefs that have been modified
   migratePref("browser.newtabpage.rows", rows => {
     // Just disable top sites if rows are not desired
     if (rows <= 0) {
       Services.prefs.setBoolPref("browser.newtabpage.activity-stream.showTopSites", false);
     } else {
       Services.prefs.setIntPref("browser.newtabpage.activity-stream.topSitesRows", rows);
@@ -160,21 +138,16 @@ function onBrowserReady() {
  */
 function observe(subject, topic, data) {
   switch (topic) {
     case BROWSER_READY_NOTIFICATION:
       Services.obs.removeObserver(observe, BROWSER_READY_NOTIFICATION);
       // Avoid running synchronously during this event that's used for timing
       Services.tm.dispatchToMainThread(() => onBrowserReady());
       break;
-    case PREF_CHANGED_TOPIC:
-      if (data === ACTIVITY_STREAM_ENABLED_PREF) {
-        onPrefChanged();
-      }
-      break;
   }
 }
 
 // The functions below are required by bootstrap.js
 
 this.install = function install(data, reason) {};
 
 this.startup = function startup(data, reason) {
@@ -196,19 +169,16 @@ this.shutdown = function shutdown(data, 
   // Uninitialize Activity Stream
   startupData = null;
   startupReason = null;
   uninit(reason);
 
   // Stop waiting for browser to be ready
   if (waitingForBrowserReady) {
     Services.obs.removeObserver(observe, BROWSER_READY_NOTIFICATION);
-  } else {
-    // Stop listening to the pref that enables Activity Stream
-    Services.prefs.removeObserver(ACTIVITY_STREAM_ENABLED_PREF, observe);
   }
 
   // Unload any add-on modules that might might have been imported
   modulesToUnload.forEach(Cu.unload);
 };
 
 this.uninstall = function uninstall(data, reason) {
   if (activityStream) {

--- a/browser/extensions/activity-stream/test/functional/mochitest/browser_as_load_location.js
+++ b/browser/extensions/activity-stream/test/functional/mochitest/browser_as_load_location.js
@@ -31,23 +31,8 @@ async function checkActivityStreamLoads(
 // Run a first time not from a preloaded browser
 add_task(async function checkActivityStreamNotPreloadedLoad() {
   gBrowser.removePreloadedBrowser();
   await checkActivityStreamLoads();
 });
 
 // Run a second time from a preloaded browser
 add_task(checkActivityStreamLoads);
-
-// Test with activity stream off
-async function checkNotActivityStreamLoads() {
-  await SpecialPowers.pushPrefEnv({set: [["browser.newtabpage.activity-stream.enabled", false]]});
-  await checkNewtabLoads("body:not(.activity-stream)", "Got <body> Element not for activity-stream");
-}
-
-// Run a first time not from a preloaded browser
-add_task(async function checkNotActivityStreamNotPreloadedLoad() {
-  gBrowser.removePreloadedBrowser();
-  await checkNotActivityStreamLoads();
-});
-
-// Run a second time from a preloaded browser
-add_task(checkNotActivityStreamLoads);

--- a/browser/extensions/activity-stream/test/functional/mochitest/head.js
+++ b/browser/extensions/activity-stream/test/functional/mochitest/head.js
@@ -5,22 +5,16 @@ ChromeUtils.defineModuleGetter(this, "Pl
 
 function popPrefs() {
   return SpecialPowers.popPrefEnv();
 }
 function pushPrefs(...prefs) {
   return SpecialPowers.pushPrefEnv({set: prefs});
 }
 
-// Activity Stream tests expect it to be enabled, and make sure to clear out any
-// preloaded browsers that might have about:newtab that we don't want to test
-const ACTIVITY_STREAM_PREF = "browser.newtabpage.activity-stream.enabled";
-pushPrefs([ACTIVITY_STREAM_PREF, true]);
-gBrowser.removePreloadedBrowser();
-
 async function clearHistoryAndBookmarks() { // eslint-disable-line no-unused-vars
   await PlacesUtils.bookmarks.eraseEverything();
   await PlacesUtils.history.clear();
 }
 
 /**
  * Helper to wait for potentially preloaded browsers to "load" where a preloaded
  * page has already loaded and won't trigger "load", and a "load"ed page might

--- a/browser/extensions/onboarding/test/browser/browser_onboarding_accessibility.js
+++ b/browser/extensions/onboarding/test/browser/browser_onboarding_accessibility.js
@@ -25,35 +25,16 @@ add_task(async function test_onboarding_
       "Onboarding button semantically controls an overlay dialog");
     is(button.firstChild.getAttribute("role"), "presentation",
       "Onboarding button icon should have presentation only semantics");
   });
 
   await BrowserTestUtils.removeTab(tab);
 });
 
-add_task(async function test_onboarding_overlay_button_no_activity_steam() {
-  /* https://bugzilla.mozilla.org/show_bug.cgi?id=1393564 */
-  resetOnboardingDefaultState();
-  Preferences.set("browser.newtabpage.activity-stream.enabled", false);
-
-  info("Wait for onboarding overlay loaded");
-  let tab = await openTab(ABOUT_NEWTAB_URL);
-  let browser = tab.linkedBrowser;
-  await promiseOnboardingOverlayLoaded(browser);
-
-  info("Click on overlay button and ensure dialog opens");
-  await BrowserTestUtils.synthesizeMouseAtCenter("#onboarding-overlay-button",
-                                                 {}, browser);
-  await promiseOnboardingOverlayOpened(browser);
-
-  Preferences.reset("browser.newtabpage.activity-stream.enabled");
-  await BrowserTestUtils.removeTab(tab);
-});
-
 add_task(async function test_onboarding_notification_bar() {
   resetOnboardingDefaultState();
   skipMuteNotificationOnFirstSession();
 
   let tab = await openTab(ABOUT_NEWTAB_URL);
   await promiseOnboardingOverlayLoaded(tab.linkedBrowser);
   await promiseTourNotificationOpened(tab.linkedBrowser);
 

--- a/dom/base/test/browser_messagemanager_loadprocessscript.js
+++ b/dom/base/test/browser_messagemanager_loadprocessscript.js
@@ -2,23 +2,18 @@ var ppmm = Cc["@mozilla.org/parentproces
            .getService(Ci.nsIMessageBroadcaster);
 ppmm.QueryInterface(Ci.nsIProcessScriptLoader);
 
 const BASE_NUMBER_OF_PROCESSES = 3;
 function checkBaseProcessCount(description) {
   const {childCount} = ppmm;
   // With preloaded activity-stream, process count is a bit undeterministic, so
   // allow for some variation
-  if (Services.prefs.getBoolPref("browser.newtabpage.activity-stream.enabled")) {
-    const extraCount = BASE_NUMBER_OF_PROCESSES + 1;
-    ok(childCount === BASE_NUMBER_OF_PROCESSES || childCount === extraCount, `${description} (${BASE_NUMBER_OF_PROCESSES} or ${extraCount})`);
-  }
-  else {
-    is(childCount, BASE_NUMBER_OF_PROCESSES, `${description} (${BASE_NUMBER_OF_PROCESSES})`);
-  }
+  const extraCount = BASE_NUMBER_OF_PROCESSES + 1;
+  ok(childCount === BASE_NUMBER_OF_PROCESSES || childCount === extraCount, `${description} (${BASE_NUMBER_OF_PROCESSES} or ${extraCount})`);
 }
 
 function processScript() {
   let cpmm = Components.classes["@mozilla.org/childprocessmessagemanager;1"]
            .getService(Components.interfaces.nsISyncMessageSender);
   if (cpmm !== this) {
     dump("Test failed: wrong global object\n");
     return;