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

chrome/browser/engagement/site_engagement_eviction_policy.cc

Index: chrome/browser/engagement/site_engagement_eviction_policy.cc
diff --git a/chrome/browser/engagement/site_engagement_eviction_policy.cc b/chrome/browser/engagement/site_engagement_eviction_policy.cc
index 02b2152ef054d0dbd11310b51f8c53d63038c163..43ef3dff1b46e55363011ae89dd6c3e3855b3834 100644
--- a/chrome/browser/engagement/site_engagement_eviction_policy.cc
+++ b/chrome/browser/engagement/site_engagement_eviction_policy.cc
@@ -2,12 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "chrome/browser/engagement/site_engagement_eviction_policy.h"
+
 #include "base/barrier_closure.h"
+#include "base/command_line.h"
 #include "chrome/browser/browser_process.h"
-#include "chrome/browser/engagement/site_engagement_eviction_policy.h"
 #include "chrome/browser/engagement/site_engagement_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_manager.h"
+#include "chrome/common/chrome_switches.h"
 #include "content/public/browser/browser_thread.h"
 #include "storage/browser/quota/usage_tracker.h"
 
@@ -102,6 +105,12 @@ GURL GetSiteEngagementEvictionOriginOnUIThread(
 
 }  // namespace
 
+// static
+bool SiteEngagementEvictionPolicy::IsEnabled() {
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableSiteEngagementEvictionPolicy);
+}
+
 SiteEngagementEvictionPolicy::SiteEngagementEvictionPolicy(
     storage::StorageType type,
     storage::QuotaManager* manager,