Bug 1648223 - Enable the Experimental Preferences by default. r=mstriemer,preferences-reviewers,ntim

Differential Revision: https://phabricator.services.mozilla.com/D81111

browser/app/profile/firefox.js

@@ -754,7 +754,11 @@ pref("plugins.favorfallback.rules", "nosrc,video");
 
 // Toggling Search bar on and off in about:preferences
 pref("browser.preferences.search", true);
+#if defined(NIGHTLY_BUILD)
+pref("browser.preferences.experimental", true);
+#else
 pref("browser.preferences.experimental", false);
+#endif
 pref("browser.preferences.defaultPerformanceSettings.enabled", true);
 
 pref("browser.download.show_plugins_in_list", true);

browser/components/preferences/preferences.js

@@ -84,14 +84,17 @@ function init_all() {
   register_module("paneSearch", gSearchPane);
   register_module("panePrivacy", gPrivacyPane);
   register_module("paneContainers", gContainersPane);
-  if (Services.prefs.getBoolPref("identity.fxaccounts.enabled")) {
-    document.getElementById("category-sync").hidden = false;
-    register_module("paneSync", gSyncPane);
-  }
   if (Services.prefs.getBoolPref("browser.preferences.experimental")) {
     document.getElementById("category-experimental").hidden = false;
     register_module("paneExperimental", gExperimentalPane);
   }
+  // The Sync category needs to be the last of the "real" categories
+  // registered and inititalized since many tests wait for the
+  // "sync-pane-loaded" observer notification before starting the test.
+  if (Services.prefs.getBoolPref("identity.fxaccounts.enabled")) {
+    document.getElementById("category-sync").hidden = false;
+    register_module("paneSync", gSyncPane);
+  }
   register_module("paneSearchResults", gSearchResultsPane);
   gSearchResultsPane.init();
   gMainPane.preInit();

toolkit/components/featuregates/docs/index.rst

@@ -15,21 +15,25 @@ Feature Definitions
 
 All features must have a definition, specified in
 ``toolkit/components/featuregates/Features.toml``. These definitions include
-data such as title and description (to be shown to users), and bug numbers (to
-track the development of the feature over time). Here is an example feature
-definition with an id of ``demo-feature``:
+data such as references to title and description strings (to be shown to users),
+and bug numbers (to track the development of the feature over time). Here is an
+example feature definition with an id of ``demo-feature``:
 
 .. code-block:: toml
 
    [demo-feature]
-   title = "Demo Feature"
-   description = "A no-op feature to demo the feature gate system."
+   title = "experimental-features-demo-feature"
+   description = "experimental-features-demo-feature-description"
    restart-required = false
    bug-numbers = [1479127]
    type = boolean
    is-public = {default = false, nightly = true}
    default-value = {default = false, nightly = true}
 
+The references defined in the `title` and `description` values point to strings
+stored in ``toolkit/locales/en-US/toolkit/featuregates/features.ftl``. The `title`
+string should specify the user-facing string as the `label` attribute.
+
 .. _targeted value:
 
 Targeted values
@@ -83,17 +87,40 @@ Fields
 ------
 
 title
-    Required. A human readable name for the feature, meant to be shown to
-    users. Should fit onto a single line.
+    Required. The string ID of the human readable name for the feature, meant to be shown to
+    users. Should fit onto a single line. The actual string should be defined in
+    ``toolkit/locales/en-US/toolkit/featuregates/features.ftl`` with the user-facing value
+    defined as the `label` attribute of the string.
 
 description
-    Required. A human readable description for the feature, meant to be shown to
-    users. Should be at most a paragraph.
+    Required. The string ID of the human readable description for the feature, meant to be shown to
+    users. Should be at most a paragraph. The actual string should be defined in
+    ``toolkit/locales/en-US/toolkit/featuregates/features.ftl``.
 
 description-links
     Optional. A dictionary of key-value pairs that are referenced in the description. The key
     name must appear in the description localization text as
-    <a data-l10n-name="key-name">.
+    <a data-l10n-name="key-name">. For example in Features.toml:
+
+.. code-block:: toml
+
+   [demo-feature]
+   title = "experimental-features-demo-feature"
+   description = "experimental-features-demo-feature-description"
+   description-links = {exampleCom = "https://example.com", exampleOrg = "https://example.org"}
+   restart-required = false
+   bug-numbers = [1479127]
+   type = boolean
+   is-public = {default = false, nightly = true}
+   default-value = {default = false, nightly = true}
+
+and in features.ftl:
+
+.. code-block:: fluent
+
+   experimental-features-demo-feature =
+       .label = Example Demo Feature
+   experimental-features-demo-feature-description = Example demo feature that can point to <a data-l10n-name="exampleCom">.com</a> links and <a data-l10n-name="exampleOrg">.org</a> links.
 
 bug-numbers
     Required. A list of bug numbers related to this feature. This should