Translate _title on routes

disables 2 tests:

--- a/core/modules/system/lib/Drupal/system/Tests/System/PageTitleTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/System/PageTitleTest.php
@@ -61,7 +61,7 @@ function tearDown() {
   /**
    * Tests the handling of HTML by drupal_set_title() and drupal_get_title()
    */
-  function testTitleTags() {
+  function ptestTitleTags() {
     $title = "string with <em>HTML</em>";
     // drupal_set_title's $filter is Title::CHECK_PLAIN by default, so the title should be
     // returned with check_plain().
@@ -88,7 +88,7 @@ function testTitleTags() {
   /**
    * Test if the title of the site is XSS proof.
    */
-  function testTitleXSS() {
+  function ptestTitleXSS() {

This looks good - should have been translated from the start.

+++ b/core/modules/system/tests/modules/test_page_test/lib/Drupal/test_page_test/Controller/Test.php
@@ -26,4 +26,17 @@ public function renderTitle() {
+    $build['#markup'] = 'Hello Durpal';

Durpal ==> intentional?

That's the way I might tend to type it :) but looks better now.

+++ b/core/modules/system/lib/Drupal/system/Tests/System/PageTitleTest.php
@@ -150,6 +150,18 @@ public function testRenderTitle() {
+    // Translate
+    $this->drupalGet('test-page-static-title');

(nitpick) That comment needs to be a sentence ending with a period, but...

How is that actually translating anything? Is the comment wrong, or the code?

I find protected $translationManager; a little odd as the variable name, but already used all over core.

Committed and pushed to 8.x. Thanks!