Fix the multi-threaded access to WeakPtr<BrowsingDataRemoverImpl>

chrome/browser/browsing_data/browsing_data_remover_impl.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_BROWSING_DATA_BROWSING_DATA_REMOVER_IMPL_H_
 #define CHROME_BROWSER_BROWSING_DATA_BROWSING_DATA_REMOVER_IMPL_H_
 
 #include <stdint.h>
 
 #include <queue>
@@ skipping 187 matching lines @@
 
   // Notifies observers and transitions to the idle state.
   void Notify();
 
   // Checks if we are all done, and if so, calls Notify().
   void NotifyIfDone();
 
   // Returns true if we're all done.
   bool AllDone();
 
+  // Retrieve a UI thread-bound weak pointer to this BrowsingDataRemoverImpl.
+  base::WeakPtr<BrowsingDataRemoverImpl> GetWeakPtr();
+
   // The browser context we're to remove from.
   content::BrowserContext* browser_context_;
 
   // A delegate to delete the embedder-specific data.
   std::unique_ptr<BrowsingDataRemoverDelegate> embedder_delegate_;
 
   // Start time to delete from.
   base::Time delete_begin_;
 
   // End time to delete to.
@@ skipping 33 matching lines @@
 
   // We do not own this.
   content::StoragePartition* storage_partition_for_testing_ = nullptr;
 
   base::WeakPtrFactory<BrowsingDataRemoverImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowsingDataRemoverImpl);
 };
 
 #endif  // CHROME_BROWSER_BROWSING_DATA_BROWSING_DATA_REMOVER_IMPL_H_