Remove ChromeBrowserProvider::IsOffTheRecordSessionActive().

ios/chrome/browser/downstream_chromium_browser_provider.h

 // Copyright 2016 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_DOWNSTREAM_CHROMIUM_BROWSER_PROVIDER_H_
 #define IOS_CHROME_BROWSER_DOWNSTREAM_CHROMIUM_BROWSER_PROVIDER_H_
 
 #include "ios/chrome/browser/providers/chromium_browser_provider.h"
 
 // DownstreamChromiumBrowserProvider contains provider implementations that will
 // eventually move into the upstream ChromiumBrowserProvider, but currently
 // cannot move because they have internal dependencies.
 class DownstreamChromiumBrowserProvider : public ChromiumBrowserProvider {
  public:
   DownstreamChromiumBrowserProvider();
   ~DownstreamChromiumBrowserProvider() override;
 
  private:
   // ChromeBrowserProvider implementations.  All of these will move upstream
   // into ChromiumBrowserProvider eventually, and from there callers will be
   // converted to not go through the provider API at all.
-  bool IsOffTheRecordSessionActive() override;
   void GetFaviconForURL(
       ios::ChromeBrowserState* browser_state,
       const GURL& page_url,
       const std::vector<int>& desired_sizes_in_pixel,
       const favicon_base::FaviconResultsCallback& callback) const override;
   std::unique_ptr<sync_sessions::SyncedWindowDelegatesGetter>
   CreateSyncedWindowDelegatesGetter(
       ios::ChromeBrowserState* browser_state) override;
 
   DISALLOW_COPY_AND_ASSIGN(DownstreamChromiumBrowserProvider);
 };
 
 #endif  // IOS_CHROME_BROWSER_DOWNSTREAM_CHROMIUM_BROWSER_PROVIDER_H_