Regression: Using [...] to change language does not activate apply button

Bug: 53736
Change-Id: If52beb73f9f3f74cde63bd846974540682066ab6

resources/js/ext.uls.displaysettings.js

@@ -107,8 +107,13 @@
 			this.prepareLanguages();
 			this.prepareUIFonts();
 			this.prepareContentFonts();
+
+			// Usually this is already loaded, but when changing language it
+			// might not be.
 			$.i18n().locale = this.uiLanguage;
-			this.i18n();
+			mw.uls.loadLocalization( this.uiLanguage )
+				.done( $.proxy( this.i18n, this ) );
+
 			this.$webfonts.refresh();
 			this.listen();
 			this.dirty = false;
@@ -316,15 +321,13 @@
 					}
 				},
 				onSelect: function ( langCode ) {
-					displaySettings.markDirty();
 					displaySettings.uiLanguage = langCode;
-					displaySettings.$parent.show();
-					displaySettings.prepareUIFonts();
-					displaySettings.prepareLanguages();
-					// set the language for the settings panel so that webfonts
-					// are correctly applied.
 					displaySettings.$template.attr( 'lang', langCode );
-					displaySettings.preview( langCode );
+					// This re-renders the whole thing
+					displaySettings.$parent.show();
+					// And the only thing we need to take care of is to enable
+					// the apply button
+					displaySettings.markDirty();
 				},
 				quickList: function () {
 					return mw.uls.getFrequentLanguageList();

tests/browser/features/step_definitions/common_steps.rb

@@ -31,6 +31,15 @@ Given(/^the content language is "(.*?)"$/) do |language|
 	actual.should == code
 end
 
+Given(/^the interface language is "(.*?)"$/) do |language|
+	# phantomjs needs little bit time because it executes the script before
+	# the page is fully loaded
+	sleep 0.5;
+	code = language_to_code(language)
+	actual = @browser.execute_script( "return mw.config.get( 'wgUserLanguage' )" )
+	actual.should == code
+end
+
 def language_to_code(language)
 	case language
 	when 'German'

tests/browser/features/uls_settings_panel.feature

@@ -63,3 +63,13 @@ Feature: ULS settings panel
     Given I temporarily use "Finnish" as the interface language
     When I open "Language" panel of language settings
     Then I see "English (sama kuin sisällön)" as the name of the content language
+
+  @login @reset-preferences-after
+  Scenario: Selecting language via [...] button
+
+    Given I am logged in
+    When I open "Language" panel of language settings
+      And I click the button with the ellipsis
+      And I use the panel to change my interface language to "German"
+      And I apply the changes
+    Then the interface language is "German"