Settings: When saved password check closes, focus on export dialog

The bug in refers to the fact that before this change, pressing 'ENTER'
with the exportPasswords dialog up would cause a password check
initially, however if the user cancelled the password check prompt,
they will again see the exportPasswords but this time 'ENTER' does
nothing.

hcarmona@ pointed out that this is part of a broader accessibility
issue on this page, namely that the password prompts' closing doesn't
put focus back on the element that triggered it to open. This can lead
to a confusing and difficult UX for users who are using tab to navigate
through the interactive elements on the page.

I ran through a wide range of use cases affected by this change and
recorded them, mostly captured in [1]. Note that the transition at
0:29-0:30 in [1] resulted from pressing enter at the
passwords-export-dialog.

I recorded successful password entries ([2], [3], [4]) separately
because if they are done in close succession, the auth token is
reused and the password prompt is skipped, which negates defeats the
purpose of the recording.

[1] https://drive.google.com/file/d/13naHaZSf7hG3pC09XaO7WW4bmDmmhYW6/view
[2] Successful password prompt from passwords-export-dialog:
https://drive.google.com/file/d/1LLN0dJ8NY54zSTOoZL6F9AcPSFHF0EFy/view
[3] Successful password prompt from password-list-item:
https://drive.google.com/file/d/1hIDOFFrEMRClFlT0VfVTXtyw-YweIfsp/view
[4] Successful password entry from password-edit-dialog
https://drive.google.com/file/d/1XJaGTrmDm4dOnc6a1tQyKnNxaHWU_NzR/view

Bug: 989449
Change-Id: Ic5a363d217cb70e76aa6acb5104ec2fea3a00b4c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1731733
Commit-Queue: Jordy Greenblatt <jordynass@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683788}

chrome/browser/resources/settings/autofill_page/passwords_section.js

@@ -156,11 +156,14 @@ Polymer({
   },
 
   /**
-   * The element to return focus to, when the currently active dialog is
-   * closed.
-   * @private {?HTMLElement}
+   * A stack of the elements that triggered dialog to open and should therefore
+   * receive focus when that dialog is closed. The bottom of the stack is the
+   * element that triggered the earliest open dialog and top of the stack is the
+   * element that triggered the most recent (i.e. active) dialog. If no dialog
+   * is open, the stack is empty.
+   * @private {!Array<Element>}
    */
-  activeDialogAnchor_: null,
+  activeDialogAnchorStack_: [],
 
   /**
    * @type {PasswordManagerProxy}
@@ -210,7 +213,7 @@ Polymer({
       this.tokenRequestManager_ = new settings.BlockingRequestManager();
     } else {
       this.tokenRequestManager_ = new settings.BlockingRequestManager(
-          () => this.showPasswordPromptDialog_ = true);
+          this.openPasswordPromptDialog_.bind(this));
     }
     // </if>
 
@@ -273,6 +276,12 @@ Polymer({
 
   onPasswordPromptClosed_: function() {
     this.showPasswordPromptDialog_ = false;
+    cr.ui.focusWithoutInk(assert(this.activeDialogAnchorStack_.pop()));
+  },
+
+  openPasswordPromptDialog_: function() {
+    this.activeDialogAnchorStack_.push(getDeepActiveElement());
+    this.showPasswordPromptDialog_ = true;
   },
   // </if>
 
@@ -290,8 +299,7 @@ Polymer({
   /** @private */
   onPasswordEditDialogClosed_: function() {
     this.showPasswordEditDialog_ = false;
-    cr.ui.focusWithoutInk(assert(this.activeDialogAnchor_));
-    this.activeDialogAnchor_ = null;
+    cr.ui.focusWithoutInk(assert(this.activeDialogAnchorStack_.pop()));
 
     // Trigger a re-evaluation of the activePassword as the visibility state of
     // the password might have changed.
@@ -376,7 +384,7 @@ Polymer({
     this.activePassword =
         /** @type {!PasswordListItemElement} */ (event.detail.listItem);
     menu.showAt(target);
-    this.activeDialogAnchor_ = target;
+    this.activeDialogAnchorStack_.push(target);
   },
 
   /**
@@ -389,7 +397,7 @@ Polymer({
         /** @type {!HTMLElement} */ (this.$$('#exportImportMenuButton'));
 
     menu.showAt(target);
-    this.activeDialogAnchor_ = target;
+    this.activeDialogAnchorStack_.push(target);
   },
 
   /**
@@ -413,8 +421,7 @@ Polymer({
   /** @private */
   onPasswordsExportDialogClosed_: function() {
     this.showPasswordsExportDialog_ = false;
-    cr.ui.focusWithoutInk(assert(this.activeDialogAnchor_));
-    this.activeDialogAnchor_ = null;
+    cr.ui.focusWithoutInk(assert(this.activeDialogAnchorStack_.pop()));
   },
 
   /**