[Sync::Consent] Don't link UserEventService if separate datatype is used.

Previously ConsentAuditor did get UserEventService even when the
separate consents datatype was used. In this CL, the UserEventService is
just not requested from ConsentAuditor factory at all in this case (on
all platforms). Also DCHECKs in ConsentAuditor are adjusted to check only
the correct dependency based on the feature.

Bug: 851438
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I756e595b826e084d1b2f9905d2827cae1160fedd
Reviewed-on: https://chromium-review.googlesource.com/1124333Reviewed-by: Markus Heintz <markusheintz@chromium.org>
Commit-Queue: vitaliii <vitaliii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572580}

chrome/browser/consent_auditor/consent_auditor_factory.cc

@@ -51,7 +51,8 @@ KeyedService* ConsentAuditorFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
   Profile* profile = static_cast<Profile*>(context);
 
-  std::unique_ptr<syncer::ConsentSyncBridge> bridge;
+  std::unique_ptr<syncer::ConsentSyncBridge> consent_sync_bridge;
+  syncer::UserEventService* user_event_service = nullptr;
   if (base::FeatureList::IsEnabled(switches::kSyncUserConsentSeparateType)) {
     syncer::OnceModelTypeStoreFactory store_factory =
         browser_sync::ProfileSyncService::GetModelTypeStoreFactory(
@@ -61,13 +62,15 @@ KeyedService* ConsentAuditorFactory::BuildServiceInstanceFor(
             syncer::USER_CONSENTS,
             base::BindRepeating(&syncer::ReportUnrecoverableError,
                                 chrome::GetChannel()));
-    bridge = std::make_unique<syncer::ConsentSyncBridgeImpl>(
+    consent_sync_bridge = std::make_unique<syncer::ConsentSyncBridgeImpl>(
         std::move(store_factory), std::move(change_processor));
+  } else {
+    user_event_service =
+        browser_sync::UserEventServiceFactory::GetForProfile(profile);
   }
-  // TODO(vitaliii): Don't create UserEventService when it won't be used.
+
   return new consent_auditor::ConsentAuditor(
-      profile->GetPrefs(), std::move(bridge),
-      browser_sync::UserEventServiceFactory::GetForProfile(profile),
+      profile->GetPrefs(), std::move(consent_sync_bridge), user_event_service,
       // The browser version and locale do not change runtime, so we can pass
       // them directly.
       version_info::GetVersionNumber(),

components/consent_auditor/consent_auditor.cc

@@ -90,11 +90,12 @@ ConsentAuditor::ConsentAuditor(
       user_event_service_(user_event_service),
       app_version_(app_version),
       app_locale_(app_locale) {
-  DCHECK(!IsSeparateConsentTypeEnabled() || consent_sync_bridge_);
+  if (IsSeparateConsentTypeEnabled()) {
+    DCHECK(consent_sync_bridge_);
+  } else {
+    DCHECK(user_event_service_);
+  }
   DCHECK(pref_service_);
-  // TODO(vitaliii): Don't require user_event_service when the separate datatype
-  // is enabled.
-  DCHECK(user_event_service_);
 }
 
 ConsentAuditor::~ConsentAuditor() {}

ios/chrome/browser/consent_auditor/consent_auditor_factory.cc

@@ -57,12 +57,9 @@ std::unique_ptr<KeyedService> ConsentAuditorFactory::BuildServiceInstanceFor(
     web::BrowserState* browser_state) const {
   ios::ChromeBrowserState* ios_browser_state =
       ios::ChromeBrowserState::FromBrowserState(browser_state);
-  // TODO(crbug.com/851438): Don't create user event service at all if it is not
-  // needed.
-  syncer::UserEventService* const user_event_service =
-      IOSUserEventServiceFactory::GetForBrowserState(ios_browser_state);
 
-  std::unique_ptr<syncer::ConsentSyncBridge> bridge;
+  std::unique_ptr<syncer::ConsentSyncBridge> consent_sync_bridge;
+  syncer::UserEventService* user_event_service = nullptr;
   if (base::FeatureList::IsEnabled(switches::kSyncUserConsentSeparateType)) {
     syncer::OnceModelTypeStoreFactory store_factory =
         browser_sync::ProfileSyncService::GetModelTypeStoreFactory(
@@ -72,12 +69,16 @@ std::unique_ptr<KeyedService> ConsentAuditorFactory::BuildServiceInstanceFor(
             syncer::USER_CONSENTS,
             base::BindRepeating(&syncer::ReportUnrecoverableError,
                                 ::GetChannel()));
-    bridge = std::make_unique<syncer::ConsentSyncBridgeImpl>(
+    consent_sync_bridge = std::make_unique<syncer::ConsentSyncBridgeImpl>(
         std::move(store_factory), std::move(change_processor));
+  } else {
+    user_event_service =
+        IOSUserEventServiceFactory::GetForBrowserState(ios_browser_state);
   }
 
   return std::make_unique<consent_auditor::ConsentAuditor>(
-      ios_browser_state->GetPrefs(), std::move(bridge), user_event_service,
+      ios_browser_state->GetPrefs(), std::move(consent_sync_bridge),
+      user_event_service,
       // The browser version and locale do not change runtime, so we can pass
       // them directly.
       version_info::GetVersionNumber(),