Add "light speed" experiment code for SafeBrowsing service.

chrome/browser/safe_browsing/safe_browsing_service.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.
 
 #include "chrome/browser/safe_browsing/safe_browsing_service.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 20 matching lines @@
 #include "chrome/browser/safe_browsing/malware_details.h"
 #include "chrome/browser/safe_browsing/ping_manager.h"
 #include "chrome/browser/safe_browsing/protocol_manager.h"
 #include "chrome/browser/safe_browsing/safe_browsing_database.h"
 #include "chrome/browser/safe_browsing/ui_manager.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/url_constants.h"
-#include "components/metrics/metrics_service.h"
 #include "components/startup_metric_utils/startup_metric_utils.h"
+#include "components/variations/variations_associated_data.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/cookie_crypto_delegate.h"
 #include "content/public/browser/cookie_store_factory.h"
 #include "content/public/browser/notification_service.h"
 #include "net/cookies/cookie_monster.h"
 #include "net/url_request/url_request_context.h"
 #include "net/url_request/url_request_context_getter.h"
 
 #if defined(OS_WIN)
 #include "chrome/installer/util/browser_distribution.h"
@@ skipping 535 matching lines @@
   // Check if any profile requires the service to be active.
   bool enable = false;
   std::map<PrefService*, PrefChangeRegistrar*>::iterator iter;
   for (iter = prefs_map_.begin(); iter != prefs_map_.end(); ++iter) {
     if (iter->first->GetBoolean(prefs::kSafeBrowsingEnabled)) {
       enable = true;
       break;
     }
   }
 
+  // TODO(asvitkine): Experimental code for measuring start up impact of SB.
+  // Remove when experimentation is complete. http://crbug.com/450037
+  if (!variations::GetVariationParamValue("LightSpeed", "DisableSB").empty())
+    enable = false;
+
   if (enable)
     Start();
   else
     Stop(false);
 
 #if defined(FULL_SAFE_BROWSING)
   if (csd_service_)
     csd_service_->SetEnabledAndRefreshState(enable);
   if (download_service_)
     download_service_->SetEnabled(enable);
 #endif
 }