[AiS] Add prefetching for Answers images.

chrome/browser/autocomplete/base_search_provider.h

Index: chrome/browser/autocomplete/base_search_provider.h
diff --git a/chrome/browser/autocomplete/base_search_provider.h b/chrome/browser/autocomplete/base_search_provider.h
index 3072d028f20063ac8e801a34387173948914b78e..75ec5e6a35f434d9c9e5ea5b223f3e7c60aca490 100644
--- a/chrome/browser/autocomplete/base_search_provider.h
+++ b/chrome/browser/autocomplete/base_search_provider.h
@@ -28,6 +28,7 @@ class SuggestionDeletionHandler;
 class TemplateURL;
 
 namespace base {
+class DictionaryValue;
 class ListValue;
 class Value;
 }
@@ -434,6 +435,9 @@ class BaseSearchProvider : public AutocompleteProvider,
                            bool is_keyword_result,
                            Results* results);
 
+  // Prefetches any images in Answers results.
+  void PrefetchAnswersImages(const base::DictionaryValue* answers_json);
+
   // Called at the end of ParseSuggestResults to rank the |results|.
   virtual void SortResults(bool is_keyword,
                            const base::ListValue* relevances,