Clear browsing data from ContentSuggestionService only if exists.

chrome/browser/ntp_snippets/content_suggestions_service_factory.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 CHROME_BROWSER_NTP_SNIPPETS_CONTENT_SUGGESTIONS_SERVICE_FACTORY_H_
 #define CHROME_BROWSER_NTP_SNIPPETS_CONTENT_SUGGESTIONS_SERVICE_FACTORY_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class Profile;
 
 namespace base {
 template <typename T>
 struct DefaultSingletonTraits;
 }  // namespace base
 
 namespace ntp_snippets {
 class ContentSuggestionsService;
 }  // namespace ntp_snippets
 
 class ContentSuggestionsServiceFactory
     : public BrowserContextKeyedServiceFactory {
  public:
   static ContentSuggestionsServiceFactory* GetInstance();
   static ntp_snippets::ContentSuggestionsService* GetForProfile(
       Profile* profile);
+  static ntp_snippets::ContentSuggestionsService* GetForProfileIfExists(
+      Profile* profile);
 
  private:
   friend struct base::DefaultSingletonTraits<ContentSuggestionsServiceFactory>;
 
   ContentSuggestionsServiceFactory();
   ~ContentSuggestionsServiceFactory() override;
 
   // BrowserContextKeyedServiceFactory implementation.
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
 
   DISALLOW_COPY_AND_ASSIGN(ContentSuggestionsServiceFactory);
 };
 
 #endif  // CHROME_BROWSER_NTP_SNIPPETS_CONTENT_SUGGESTIONS_SERVICE_FACTORY_H_