MD Settings: Implement search URLs.

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

Index: chrome/test/data/webui/settings/settings_ui_browsertest.js
diff --git a/chrome/test/data/webui/settings/settings_ui_browsertest.js b/chrome/test/data/webui/settings/settings_ui_browsertest.js
index 7586db8aab782eeeb0186282e6fe93e4d4efdbd4..23670621c3010791ec7ed086e662f2162866ee40 100644
--- a/chrome/test/data/webui/settings/settings_ui_browsertest.js
+++ b/chrome/test/data/webui/settings/settings_ui_browsertest.js
@@ -111,6 +111,20 @@ TEST_F('SettingsUIBrowserTest', 'MAYBE_All', function() {
       assertFalse(ui.advancedOpened_);
       assertFalse(main.advancedToggleExpanded);
     });
+
+    test('URL search param propagates to search box', function() {
+      toolbar = /** @type {!CrToolbarElement} */ (ui.$$('cr-toolbar'));
+      var searchField = /** @type {CrToolbarSearchFieldElement} */ (
+          toolbar.getSearchField());
+
+      var query = 'foo';
+      settings.navigateTo(
+          settings.Route.BASIC, new URLSearchParams(`search=${query}`));
+      assertEquals(query, searchField.getSearchInput().bindValue);
+
+      settings.navigateTo(settings.Route.BASIC);
+      assertEquals('', searchField.getSearchInput().bindValue);
+    });
   });
 
   mocha.run();