Instantiate field trials for 'Leak detection' feature right before it's used.

That way the experiment group 'Enable' will only apply to those who use the
feature.

Bug: 986298
Change-Id: I282b75c43ecfd941c032a6d3f275e46fb5d5e82d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1777926
Commit-Queue: Vasilii Sukhanov <vasilii@chromium.org>
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Reviewed-by: Jan Wilken Dörrie <jdoerrie@chromium.org>
Auto-Submit: Vasilii Sukhanov <vasilii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#692054}

components/password_manager/core/browser/leak_detection/leak_detection_check_factory_impl.cc

@@ -21,13 +21,14 @@ LeakDetectionCheckFactoryImpl::TryCreateLeakCheck(
     LeakDetectionDelegateInterface* delegate,
     signin::IdentityManager* identity_manager,
     scoped_refptr<network::SharedURLLoaderFactory> url_loader_factory) const {
-  if (!base::FeatureList::IsEnabled(features::kLeakDetection))
-    return nullptr;
-
   if (!AuthenticatedLeakCheck::HasAccountForRequest(identity_manager)) {
     delegate->OnError(LeakDetectionError::kNotSignIn);
     return nullptr;
   }
+  // Instantiate the field trial right before the feature can be used. Thus,
+  // the experiment groups will only contain the users who can use the feature.
+  if (!base::FeatureList::IsEnabled(features::kLeakDetection))
+    return nullptr;
   return std::make_unique<AuthenticatedLeakCheck>(
       delegate, identity_manager, std::move(url_loader_factory));
 }

components/password_manager/core/browser/leak_detection/leak_detection_check_factory_impl_unittest.cc

@@ -49,6 +49,7 @@ TEST_F(LeakDetectionCheckFactoryImplTest, DisabledFeature) {
   base::test::ScopedFeatureList feature_list;
   feature_list.InitAndDisableFeature(features::kLeakDetection);
 
+  identity_env().SetPrimaryAccount(kTestAccount);
   EXPECT_FALSE(request_factory().TryCreateLeakCheck(
       &delegate(), identity_env().identity_manager(), url_loader_factory()));
 }