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

chrome/browser/chrome_content_browser_client.h

 // Copyright (c) 2012 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.
 
 #ifndef CHROME_BROWSER_CHROME_CONTENT_BROWSER_CLIENT_H_
 #define CHROME_BROWSER_CHROME_CONTENT_BROWSER_CLIENT_H_
 
 #include <set>
 #include <string>
 #include <utility>
@@ skipping 153 matching lines @@
 #if defined(ENABLE_WEBRTC)
   bool AllowWebRTCIdentityCache(const GURL& url,
                                 const GURL& first_party_url,
                                 content::ResourceContext* context) override;
 #endif  // defined(ENABLE_WEBRTC)
 
   net::URLRequestContext* OverrideRequestContextForURL(
       const GURL& url,
       content::ResourceContext* context) override;
   content::QuotaPermissionContext* CreateQuotaPermissionContext() override;
+  void AddQuotaEvictionPolicies(content::BrowserContext* context,

[dominickn, 2015/09/24 00:53:42]

Nit: can there be multiple policies added/active?

[calamity, 2015/10/26 03:01:57]

Not anymore. Changed.

+                                storage::QuotaManager* quota_manager) override;
   void AllowCertificateError(
       int render_process_id,
       int render_frame_id,
       int cert_error,
       const net::SSLInfo& ssl_info,
       const GURL& request_url,
       content::ResourceType resource_type,
       bool overridable,
       bool strict_enforcement,
       bool expired_previous_decision,
@@ skipping 147 matching lines @@
   // Vector of additional ChromeContentBrowserClientParts.
   // Parts are deleted in the reverse order they are added.
   std::vector<ChromeContentBrowserClientParts*> extra_parts_;
 
   base::WeakPtrFactory<ChromeContentBrowserClient> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeContentBrowserClient);
 };
 
 #endif  // CHROME_BROWSER_CHROME_CONTENT_BROWSER_CLIENT_H_