Make GetDismissedSuggestionsForDebugging asynchronous

components/ntp_snippets/content_suggestions_service.cc

 // 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.
 
 #include "components/ntp_snippets/content_suggestions_service.h"
 
 #include <algorithm>
 #include <iterator>
 
 #include "base/bind.h"
@@ skipping 86 matching lines @@
   for (const ContentSuggestion& suggestion :
        suggestions_by_category_[category]) {
     id_category_map_.erase(suggestion.id());
   }
   suggestions_by_category_[category].clear();
   auto iterator = providers_by_category_.find(category);
   if (iterator != providers_by_category_.end())
     iterator->second->ClearCachedSuggestionsForDebugging(category);
 }
 
-std::vector<ContentSuggestion>
-ContentSuggestionsService::GetDismissedSuggestionsForDebugging(
-    Category category) {
+void ContentSuggestionsService::GetDismissedSuggestionsForDebugging(
+    Category category,
+    const DismissedSuggestionsCallback& callback) {
   auto iterator = providers_by_category_.find(category);
-  if (iterator == providers_by_category_.end())
-    return std::vector<ContentSuggestion>();
-  return iterator->second->GetDismissedSuggestionsForDebugging(category);
+  if (iterator != providers_by_category_.end())
+    iterator->second->GetDismissedSuggestionsForDebugging(category, callback);
+  else
+    callback.Run(std::vector<ContentSuggestion>());
 }
 
 void ContentSuggestionsService::ClearDismissedSuggestionsForDebugging(
     Category category) {
   auto iterator = providers_by_category_.find(category);
   if (iterator != providers_by_category_.end())
     iterator->second->ClearDismissedSuggestionsForDebugging(category);
 }
 
 void ContentSuggestionsService::DismissSuggestion(
@@ skipping 136 matching lines @@
   return true;
 }
 
 void ContentSuggestionsService::NotifyCategoryStatusChanged(Category category) {
   FOR_EACH_OBSERVER(
       Observer, observers_,
       OnCategoryStatusChanged(category, GetCategoryStatus(category)));
 }
 
 }  // namespace ntp_snippets