MD Settings: Add mechanism to restore focus after subpage exiting.

chrome/browser/resources/settings/passwords_and_forms_page/passwords_and_forms_page.js

Index: chrome/browser/resources/settings/passwords_and_forms_page/passwords_and_forms_page.js
diff --git a/chrome/browser/resources/settings/passwords_and_forms_page/passwords_and_forms_page.js b/chrome/browser/resources/settings/passwords_and_forms_page/passwords_and_forms_page.js
index 0598f0298e8f8515b7fc4ba993b5e115a4c9521c..abf59371208c617568d3b1d40b059e6d0a8bad8b 100644
--- a/chrome/browser/resources/settings/passwords_and_forms_page/passwords_and_forms_page.js
+++ b/chrome/browser/resources/settings/passwords_and_forms_page/passwords_and_forms_page.js
@@ -10,6 +10,19 @@ Polymer({
   properties: {
     /** @private Filter applied to passwords and password exceptions. */
     passwordFilter_: String,
+
+    /** @type {?Map<string, string>} */
+    focusConfig: Object,
+  },
+
+  /** @override */
+  ready: function() {
+    this.focusConfig_ = new Map();
+    this.focusConfig_.set(
+        settings.Route.AUTOFILL.path, '#autofillManagerButton .subpage-arrow');
+    this.focusConfig_.set(
+        settings.Route.MANAGE_PASSWORDS.path,
+        '#passwordManagerButton .subpage-arrow');

[Dan Beam, 2017/04/11 00:06:07]

note: this is also a thing

this.focusConfig_ = new Map([
  [settings.Route.AUTOFILL.path, '#autofillManagerButton .subpage-arrow'],
  ...
]);

[dpapad, 2017/04/11 00:18:33]

Acknowledged. I actually used that first, and then changed it to the current
version. Creating N+1 transient arrays seemed unnecessary (N is the number of
entries), when I can use set() instead.

   },
 
   /**