Back out c237f02b3578 (bug 946296) because it broke mochitest-metro-chrome

browser/metro/profile/metro.js

@@ -201,8 +201,6 @@ pref("signon.rememberSignons", true);
 pref("layout.spellcheckDefault", 1);
 
 /* extension manager and xpinstall */
-// Completely disable extensions
-pref("extensions.defaultProviders.enabled", false);
 // Disable all add-on locations other than the profile
 pref("extensions.enabledScopes", 1);
 // Auto-disable any add-ons that are "dropped in" to the profile

toolkit/mozapps/extensions/AddonManager.jsm

@@ -23,7 +23,6 @@ if ("@mozilla.org/xre/app-info;1" in Cc) {
 
 
 const PREF_BLOCKLIST_PINGCOUNTVERSION = "extensions.blocklist.pingCountVersion";
-const PREF_DEFAULT_PROVIDERS_ENABLED  = "extensions.defaultProviders.enabled";
 const PREF_EM_UPDATE_ENABLED          = "extensions.update.enabled";
 const PREF_EM_LAST_APP_VERSION        = "extensions.lastAppVersion";
 const PREF_EM_LAST_PLATFORM_VERSION   = "extensions.lastPlatformVersion";
@@ -544,22 +543,15 @@ var AddonManagerInternal = {
     } catch (e) {}
     Services.prefs.addObserver(PREF_EM_HOTFIX_ID, this, false);
 
-    let defaultProvidersEnabled = true;
-    try {
-      defaultProvidersEnabled = Services.prefs.getBoolPref(PREF_DEFAULT_PROVIDERS_ENABLED);
-    } catch (e) {}
-
     // Ensure all default providers have had a chance to register themselves
-    if (defaultProvidersEnabled) {
-      DEFAULT_PROVIDERS.forEach(function(url) {
-        try {
-          Components.utils.import(url, {});
-        }
-        catch (e) {
-          ERROR("Exception loading default provider \"" + url + "\"", e);
-        }
-      });
-    }
+    DEFAULT_PROVIDERS.forEach(function(url) {
+      try {
+        Components.utils.import(url, {});
+      }
+      catch (e) {
+        ERROR("Exception loading default provider \"" + url + "\"", e);
+      }
+    });
 
     // Load any providers registered in the category manager
     let catman = Cc["@mozilla.org/categorymanager;1"].

toolkit/mozapps/extensions/test/xpcshell/test_default_providers_pref.js

@@ -1,13 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-// Tests the extensions.defaultProviders.enabled pref which turns
-// off the default XPIProvider and LightweightThemeManager.
-
-function run_test() {
-  Services.prefs.setBoolPref("extensions.defaultProviders.enabled", false);
-  createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "1.9.2");
-  startupManager();
-  do_check_false(AddonManager.isInstallEnabled("application/x-xpinstall"));
-  Services.prefs.clearUserPref("extensions.defaultProviders.enabled");
-}

toolkit/mozapps/extensions/test/xpcshell/xpcshell-shared.ini

@@ -148,7 +148,6 @@ fail-if = os == "android"
 [test_corrupt.js]
 [test_corrupt_strictcompat.js]
 [test_corruptfile.js]
-[test_default_providers_pref.js]
 [test_dictionary.js]
 [test_langpack.js]
 [test_disable.js]