Password check: fixed the issue of not getting callbacks when no passwords are saved

Bug: 1070620
Change-Id: Ic966e8f21ee31af7c47dc2be9a8073cd2e6f64ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2351788Reviewed-by: Jan Wilken Dörrie <jdoerrie@chromium.org>
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Commit-Queue: Andrey Zaytsev <andzaytsev@google.com>
Auto-Submit: Andrey Zaytsev <andzaytsev@google.com>
Cr-Commit-Position: refs/heads/master@{#797231}

components/password_manager/core/browser/bulk_leak_check_service.cc

@@ -85,8 +85,15 @@ BulkLeakCheckService::~BulkLeakCheckService() = default;
 void BulkLeakCheckService::CheckUsernamePasswordPairs(
     std::vector<password_manager::LeakCheckCredential> credentials) {
   DVLOG(0) << "Bulk password check, start " << credentials.size();
-  if (credentials.empty())
+  if (credentials.empty()) {
+    // Nothing to check. Still important to go through the running state, so the
+    // observers know that the results are available.
+    state_ = State::kRunning;
+    NotifyStateChanged();
+    state_ = State::kIdle;
+    NotifyStateChanged();
     return;
+  }
   if (!metrics_reporter_)
     metrics_reporter_ = std::make_unique<MetricsReporter>();
   metrics_reporter_->OnStartCheck(credentials.size());

components/password_manager/core/browser/bulk_leak_check_service_unittest.cc

@@ -140,7 +140,10 @@ TEST_F(BulkLeakCheckServiceTest, StartWithZeroPasswords) {
   StrictMock<MockObserver> observer;
   service().AddObserver(&observer);
 
+  EXPECT_CALL(observer, OnStateChanged(BulkLeakCheckService::State::kRunning));
+  EXPECT_CALL(observer, OnStateChanged(BulkLeakCheckService::State::kIdle));
   service().CheckUsernamePasswordPairs({});
+
   EXPECT_EQ(BulkLeakCheckService::State::kIdle, service().GetState());
   EXPECT_EQ(0u, service().GetPendingChecksCount());
   EXPECT_THAT(