[Settings WebUI] Fix Simultaneous Diplay of Password

This change fixes a UI bug where a hidden password was not correctly
updated when both the <password-list-item> and <password-edit-dialog>
were setting the same password at the same time.

Bug: 910081
Change-Id: If1ac5298ceebe1f12003083d87a85d1fa66a1f71
Reviewed-on: https://chromium-review.googlesource.com/c/1354275Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612787}

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

@@ -374,7 +374,12 @@ Polymer({
   showPassword_: function(event) {
     this.passwordManager_.getPlaintextPassword(
         /** @type {!number} */ (event.detail.item.entry.id), item => {
-          event.detail.set('item.password', item.plaintextPassword);
+          // Note: We are explicitly not using event.detail.set() here, as that
+          // would not trigger notifyPath if event.detail.item.password is
+          // already equal to item.plaintextPassword. See crbug/910081 for more
+          // details.
+          event.detail.item.password = item.plaintextPassword;
+          event.detail.notifyPath('item.password');
         });
   },