Fix regression in chrome://settings/manageProfile.

When 'Allow Chrome sign-in' is turned off, navigating to
chrome://settings/manageProfile' by typing it in the omnibox leads to an
empty page. The reason for that is a failure assert in
|getEditPersonAssocControl_|. |profile-row| is inside a 'dom-if'
template with the condition |!shouldShowSyncAccountControl_|. In polymer
v3, this function gets called when at least when of its arguments is
defined. In the time where the manage profile page is loaded,
|syncStatus.syncSystemEnabled| is not defined and |profile-row| is null.

This CL ensures that |getEditPersonAssocControl_| is not called before
|syncStatus.syncSystemEnabled| gets defined.

Bug: 1083879
Change-Id: Iff6a0f3fc0ebd474c2cbf0022a524358c3f2d0a0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2207533Reviewed-by: Esmael Elmoslimany <aee@chromium.org>
Commit-Queue: Monica Basta <msalama@chromium.org>
Cr-Commit-Position: refs/heads/master@{#770506}

chrome/browser/resources/settings/people_page/people_page.html

@@ -67,7 +67,7 @@
           </settings-sync-account-control>
         </template>
         <template is="dom-if" if="[[!shouldShowSyncAccountControl_(
-            syncStatus.syncSystemEnabled)]]" restamp>
+            syncStatus.syncSystemEnabled, signinAllowed_)]]" restamp>
           <div id="profile-row" class="cr-row first two-line"
                   actionable$="[[isProfileActionable_]]"
                   on-click="onProfileTap_">
@@ -162,7 +162,8 @@ shown on non-ChromeOS platforms -->
 <if expr="not chromeos">
       <template is="dom-if" route-path="/manageProfile">
         <settings-subpage
-            associated-control="[[getEditPersonAssocControl_()]]"
+            associated-control=
+                "[[getEditPersonAssocControl_(signinAllowed_)]]"
             page-title="$i18n{editPerson}">
           <settings-manage-profile profile-name="[[profileName_]]"
               sync-status="[[syncStatus]]">