Remove call to GetBlockingPool in RLZ

ios/chrome/browser/rlz/rlz_tracker_delegate_impl.h

 // 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.
 
 #ifndef IOS_CHROME_BROWSER_RLZ_RLZ_TRACKER_DELEGATE_IMPL_H_
 #define IOS_CHROME_BROWSER_RLZ_RLZ_TRACKER_DELEGATE_IMPL_H_
 
 #include <memory>
 
 #include "base/callback.h"
@@ skipping 15 matching lines @@
   ~RLZTrackerDelegateImpl() override;
 
   static bool IsGoogleDefaultSearch(ios::ChromeBrowserState* browser_state);
   static bool IsGoogleHomepage(ios::ChromeBrowserState* browser_state);
   static bool IsGoogleInStartpages(ios::ChromeBrowserState* browser_state);
 
  private:
   // RLZTrackerDelegate implementation.
   void Cleanup() override;
   bool IsOnUIThread() override;
-  base::SequencedWorkerPool* GetBlockingPool() override;
   net::URLRequestContextGetter* GetRequestContext() override;
   bool GetBrand(std::string* brand) override;
   bool IsBrandOrganic(const std::string& brand) override;
   bool GetReactivationBrand(std::string* brand) override;
   bool ShouldEnableZeroDelayForTesting() override;
   bool GetLanguage(base::string16* language) override;
   bool GetReferral(base::string16* referral) override;
   bool ClearReferral() override;
   void SetOmniboxSearchCallback(const base::Closure& callback) override;
   void SetHomepageSearchCallback(const base::Closure& callback) override;
 
   // Called when user open an URL from the Omnibox.
   void OnURLOpenedFromOmnibox(OmniboxLog* log);
 
   base::Closure on_omnibox_search_callback_;
   std::unique_ptr<base::CallbackList<void(OmniboxLog*)>::Subscription>
       on_omnibox_url_opened_subscription_;
 
   DISALLOW_COPY_AND_ASSIGN(RLZTrackerDelegateImpl);
 };
 
 #endif  // IOS_CHROME_BROWSER_RLZ_RLZ_TRACKER_DELEGATE_IMPL_H_