MD Settings: Preserve search URL param in subpages.

chrome/test/data/webui/settings/route_tests.js

Index: chrome/test/data/webui/settings/route_tests.js
diff --git a/chrome/test/data/webui/settings/route_tests.js b/chrome/test/data/webui/settings/route_tests.js
index 302f2f57115288b60d16bbec06bbaa64eb0bd60e..7c1314b270565dee3b4c4682120b773edbb97627 100644
--- a/chrome/test/data/webui/settings/route_tests.js
+++ b/chrome/test/data/webui/settings/route_tests.js
@@ -126,6 +126,20 @@ suite('route', function() {
     assertEquals(settings.Route.BASIC, settings.getCurrentRoute());
   });
 
+  test('navigateTo respects preserveSearch optional parameter', function() {
+    var params = new URLSearchParams('search=foo');
+    settings.navigateTo(settings.Route.BASIC, params);
+    assertEquals(params.toString(), settings.getQueryParameters().toString());
+
+    settings.navigateTo(
+        settings.Route.SITE_SETTINGS, null, true /* preserveSearch */);
+    assertEquals(params.toString(), settings.getQueryParameters().toString());
+
+    settings.navigateTo(
+        settings.Route.SEARCH_ENGINES, null, false /* preserveSearch */);
+    assertEquals('', settings.getQueryParameters().toString());
+  });
+
   test('popstate flag works', function() {
     settings.navigateTo(settings.Route.BASIC);
     assertFalse(settings.lastRouteChangeWasPopstate());