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

chrome/browser/engagement/site_engagement_eviction_policy.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // 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/command_line.h"
+#include "base/metrics/field_trial.h"
+#include "base/strings/string_util.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"
 
 namespace {
 
 const int kExpectedEngagementSites = 200;
 
 // Gets the quota that an origin deserves based on its site engagement.
 int64 GetSoftQuotaForOrigin(const GURL& origin,
                             int score,
                             int total_engagement_points,
@@ skipping 64 matching lines @@
 
   if (!score_provider)
     return GURL();
 
   return DoCalculateEvictionOrigin(special_storage_policy, score_provider,
                                    exceptions, usage_map, global_quota);
 }
 
 }  // namespace
 
+// static
+bool SiteEngagementEvictionPolicy::IsEnabled() {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableSiteEngagementEvictionPolicy)) {
+    return true;
+  }
+
+  const std::string group_name = base::FieldTrialList::FindFullName(
+      SiteEngagementService::kEngagementParams);
+  return base::StartsWith(group_name, "StorageEvictionEnabled",
+                          base::CompareCase::SENSITIVE);
+}
+
 SiteEngagementEvictionPolicy::SiteEngagementEvictionPolicy(
     content::BrowserContext* browser_context)
     : browser_context_(browser_context) {}
 
 SiteEngagementEvictionPolicy::~SiteEngagementEvictionPolicy() {}
 
 void SiteEngagementEvictionPolicy::GetEvictionOrigin(
     const scoped_refptr<storage::SpecialStoragePolicy>& special_storage_policy,
     const std::set<GURL>& exceptions,
     const std::map<GURL, int64>& usage_map,
@@ skipping 12 matching lines @@
 // static
 GURL SiteEngagementEvictionPolicy::CalculateEvictionOriginForTests(
     const scoped_refptr<storage::SpecialStoragePolicy>& special_storage_policy,
     SiteEngagementScoreProvider* score_provider,
     const std::set<GURL>& exceptions,
     const std::map<GURL, int64>& usage_map,
     int64 global_quota) {
   return DoCalculateEvictionOrigin(special_storage_policy, score_provider,
                                    exceptions, usage_map, global_quota);
 }