Fixes an invalidated pointer access in NTPSnipppetsFetcher.

components/ntp_snippets/content_suggestions_service.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 COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_SERVICE_H_
 #define COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_SERVICE_H_
 
 #include <map>
 #include <memory>
 #include <set>
@@ skipping 16 matching lines @@
 class PrefService;
 class PrefRegistrySimple;
 
 namespace gfx {
 class Image;
 }  // namespace gfx
 
 namespace ntp_snippets {
 
 class NTPSnippetsService;
-class NTPSnippetsFetcher;
 
 // Retrieves suggestions from a number of ContentSuggestionsProviders and serves
 // them grouped into categories. There can be at most one provider per category.
 class ContentSuggestionsService : public KeyedService,
                                   public ContentSuggestionsProvider::Observer,
                                   public history::HistoryServiceObserver {
  public:
   // TODO(treib): All these should probably be OnceCallback.
   using ImageFetchedCallback = base::Callback<void(const gfx::Image&)>;
   using DismissedSuggestionsCallback = base::Callback<void(
@@ skipping 256 matching lines @@
   PrefService* pref_service_;
 
   UserClassifier user_classifier_;
 
   DISALLOW_COPY_AND_ASSIGN(ContentSuggestionsService);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_SERVICE_H_