Move SafeBrowsing to the blocking pool via an experiment.

chrome/browser/safe_browsing/safe_browsing_service_browsertest.cc

 // 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.
 //
 // This test creates a safebrowsing service using test safebrowsing database
 // and a test protocol manager. It is used to test logics in safebrowsing
 // service.
 
 #include <algorithm>
 
@@ skipping 238 matching lines @@
   base::hash_set<SBPrefix> download_digest_prefix_;
 };
 
 // Factory that creates TestSafeBrowsingDatabase instances.
 class TestSafeBrowsingDatabaseFactory : public SafeBrowsingDatabaseFactory {
  public:
   TestSafeBrowsingDatabaseFactory() : db_(NULL) {}
   ~TestSafeBrowsingDatabaseFactory() override {}
 
   SafeBrowsingDatabase* CreateSafeBrowsingDatabase(
+      const scoped_refptr<base::SequencedTaskRunner>& db_task_runner,
       bool enable_download_protection,
       bool enable_client_side_whitelist,
       bool enable_download_whitelist,
       bool enable_extension_blacklist,
       bool enable_side_effect_free_whitelist,
       bool enable_ip_blacklist,
       bool enabled_unwanted_software_list) override {
     db_ = new TestSafeBrowsingDatabase();
     return db_;
   }
@@ skipping 967 matching lines @@
   content::WindowedNotificationObserver observer(
       chrome::NOTIFICATION_SAFE_BROWSING_UPDATE_COMPLETE,
       content::Source<SafeBrowsingDatabaseManager>(
           sb_service_->database_manager().get()));
   BrowserThread::PostTask(
       BrowserThread::IO,
       FROM_HERE,
       base::Bind(&SafeBrowsingDatabaseManagerCookieTest::ForceUpdate, this));
   observer.Wait();
 }