Enable SiteEngagementEvictionPolicy behind --enable-site-eviction-policy flag.

chrome/browser/engagement/site_engagement_service.cc

Index: chrome/browser/engagement/site_engagement_service.cc
diff --git a/chrome/browser/engagement/site_engagement_service.cc b/chrome/browser/engagement/site_engagement_service.cc
index 9e7798cd6dc77adce456d32667de46076d3a7149..afbc1472d2b717aa28297b992a245683b934f57c 100644
--- a/chrome/browser/engagement/site_engagement_service.cc
+++ b/chrome/browser/engagement/site_engagement_service.cc
@@ -15,6 +15,7 @@
 #include "base/time/default_clock.h"
 #include "base/values.h"
 #include "chrome/browser/content_settings/host_content_settings_map_factory.h"
+#include "chrome/browser/engagement/site_engagement_eviction_policy.h"
 #include "chrome/browser/engagement/site_engagement_helper.h"
 #include "chrome/browser/engagement/site_engagement_service_factory.h"
 #include "chrome/common/chrome_switches.h"
@@ -250,16 +251,20 @@ SiteEngagementService* SiteEngagementService::Get(Profile* profile) {
 
 // static
 bool SiteEngagementService::IsEnabled() {
-  const std::string group_name =
-      base::FieldTrialList::FindFullName(kEngagementParams);
+  // If the engagement service or any of its dependencies are force-enabled,
+  // return true immediately.
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableSiteEngagementService)) {
+          switches::kEnableSiteEngagementService) ||
+      SiteEngagementEvictionPolicy::IsEnabled()) {
     return true;
   }
+
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kDisableSiteEngagementService)) {
     return false;
   }
+  const std::string group_name =
+      base::FieldTrialList::FindFullName(kEngagementParams);
   return base::StartsWith(group_name, "Enabled", base::CompareCase::SENSITIVE);
 }