[MD settings] set scroll target for custom word spellings subpage

chrome/browser/resources/settings/languages_page/edit_dictionary_page.js

Index: chrome/browser/resources/settings/languages_page/edit_dictionary_page.js
diff --git a/chrome/browser/resources/settings/languages_page/edit_dictionary_page.js b/chrome/browser/resources/settings/languages_page/edit_dictionary_page.js
index c8c3939de95c0f005991d606028e46ab3c85d682..162641be47e6a85d8fe0877cf8e19d1b917e6e2f 100644
--- a/chrome/browser/resources/settings/languages_page/edit_dictionary_page.js
+++ b/chrome/browser/resources/settings/languages_page/edit_dictionary_page.js
@@ -9,10 +9,21 @@
 Polymer({
   is: 'settings-edit-dictionary-page',
 
+  behaviors: [settings.GlobalScrollTargetBehavior],
+
   properties: {
     /** @private {string} */
     newWordValue_: String,
 
+    /**
+     * Needed by GlobalScrollTargetBehavior.
+     * @override
+     */
+    subpageRoute: {
+      type: Object,
+      value: settings.Route.EDIT_DICTIONARY,
+    },
+
     /** @private {!Array<string>} */
     words_: {
       type: Array,