[Signin][Android] Check for child accounts on SigninChecker creation

(cherry picked from commit 1a83160)

Bug: b/40284908
Change-Id: I64f20ae601028987af1791c757e218e18e0ddd31
Fixed: b/343017102
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5575127
Commit-Queue: Samar Chehade-Lepleux <samarchehade@google.com>
Auto-Submit: Samar Chehade-Lepleux <samarchehade@google.com>
Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Cr-Original-Commit-Position: refs/heads/main@{#1306687}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5575755
Commit-Queue: Menghan Yang <myuu@google.com>
Commit-Queue: Boris Sazonov <bsazonov@chromium.org>
Auto-Submit: Boris Sazonov <bsazonov@chromium.org>
Reviewed-by: Menghan Yang <myuu@google.com>
Cr-Commit-Position: refs/branch-heads/6506@{#4}
Cr-Branched-From: 2c488d6-refs/heads/main@{#1306564}

chrome/browser/signin/services/android/java/src/org/chromium/chrome/browser/signin/services/SigninChecker.java

@@ -57,6 +57,9 @@ public SigninChecker(
         mAccountManagerFacade = AccountManagerFacadeProvider.getInstance();
         if (SigninFeatureMap.isEnabled(SigninFeatures.SEED_ACCOUNTS_REVAMP)) {
             mAccountManagerFacade.addObserver(this);
+            if (mAccountManagerFacade.getCoreAccountInfos().isFulfilled()) {
+                onCoreAccountInfosChanged();
+            }
         } else {
             mAccountTrackerService.addObserver(this);
         }