[iOS] Fixing account reconciler

The primary identity is now set after loading the accounts. So the
reconciler needs to start once the primary identity is set.

This patch fixes those failing tests:
-[ExternalURLSigninTestCase testSignInAddAccountCommand]
-[ExternalURLSigninTestCase testSignInReauthenticate]
-[ExternalURLSigninTestCase testSignInOneUser]

Bug: 983141
Change-Id: Iaa6c47b64573838b55035d3b78dcb50dc2901d3a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1698506
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Auto-Submit: Jérôme Lebel <jlebel@chromium.org>
Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#676857}

components/signin/core/browser/account_reconcilor.cc

@@ -250,11 +250,8 @@ void AccountReconcilor::SetIsWKHTTPSystemCookieStoreEnabled(bool is_enabled) {
 void AccountReconcilor::EnableReconcile() {
   SetState(AccountReconcilorState::ACCOUNT_RECONCILOR_SCHEDULED);
   RegisterWithAllDependencies();
-#if !defined(OS_IOS)
-  // TODO(droger): Investigate why this breaks tests on iOS.
   if (IsIdentityManagerReady())
     StartReconcile();
-#endif  // !defined(OS_IOS)
 }
 
 void AccountReconcilor::DisableReconcile(bool logout_all_accounts) {