Fix BrowsingDataCounter race condition

chrome/browser/browsing_data/site_data_counter.cc

 // Copyright 2017 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/browsing_data/site_data_counter.h"
 
 #include "chrome/browser/browsing_data/site_data_counting_helper.h"
 #include "components/browsing_data/core/pref_names.h"
 #include "content/public/browser/browser_thread.h"
 
 using content::BrowserThread;
 
 SiteDataCounter::SiteDataCounter(Profile* profile)
     : profile_(profile), weak_ptr_factory_(this) {}
 
 SiteDataCounter::~SiteDataCounter() {}
 
 const char* SiteDataCounter::GetPrefName() const {
   return browsing_data::prefs::kDeleteCookies;
 }
 
 void SiteDataCounter::Count() {
+  // Cancel existing requests.
+  weak_ptr_factory_.InvalidateWeakPtrs();
   base::Time begin = GetPeriodStart();
   auto done_callback =
       base::Bind(&SiteDataCounter::Done, weak_ptr_factory_.GetWeakPtr());
   // Use a helper class that owns itself to avoid issues when SiteDataCounter is
   // deleted before counting finished.
   auto* helper = new SiteDataCountingHelper(profile_, begin, done_callback);
   helper->CountAndDestroySelfWhenFinished();
 }
 
 void SiteDataCounter::Done(int origin_count) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   ReportResult(origin_count);
 }