[AiS] Use top local result for prefetch.

For answers prefetching, Chrome needs to know what the top search history
result for the current input is - _before_ issuing a search engine query
for that same input

BUG=406588

Review URL: https://codereview.chromium.org/470313004

Cr-Commit-Position: refs/heads/master@{#296873}

chrome/browser/autocomplete/search_provider_unittest.cc

@@ -3409,16 +3409,22 @@ TEST_F(SearchProviderTest, AnswersCache) {
   provider_->RegisterDisplayedAnswers(result);
   ASSERT_FALSE(provider_->answers_cache_.empty());
 
-  // Test that DoAnswersQuery retrieves data from cache.
-  AutocompleteInput input(base::ASCIIToUTF16("weather l"),
-                          base::string16::npos, base::string16(), GURL(),
-                          metrics::OmniboxEventProto::INVALID_SPEC, false,
-                          false, true, true,
-                          ChromeAutocompleteSchemeClassifier(&profile_));
-  provider_->DoAnswersQuery(input);
-  EXPECT_EQ(base::ASCIIToUTF16("weather los angeles"),
-            provider_->prefetch_data_.full_query_text);
-  EXPECT_EQ(base::ASCIIToUTF16("2334"), provider_->prefetch_data_.query_type);
+  // Without scored results, no answers will be retrieved.
+  AnswersQueryData answer = provider_->FindAnswersPrefetchData();
+  EXPECT_TRUE(answer.full_query_text.empty());
+  EXPECT_TRUE(answer.query_type.empty());
+
+  // Inject a scored result, which will trigger answer retrieval.
+  base::string16 query = base::ASCIIToUTF16("weather los angeles");
+  SearchSuggestionParser::SuggestResult suggest_result(
+      query, AutocompleteMatchType::SEARCH_HISTORY, query, base::string16(),
+      base::string16(), base::string16(), base::string16(), std::string(),
+      std::string(), false, 1200, false, false, query);
+  QueryForInput(ASCIIToUTF16("weather l"), false, false);
+  provider_->transformed_default_history_results_.push_back(suggest_result);
+  answer = provider_->FindAnswersPrefetchData();
+  EXPECT_EQ(base::ASCIIToUTF16("weather los angeles"), answer.full_query_text);
+  EXPECT_EQ(base::ASCIIToUTF16("2334"), answer.query_type);
 }
 
 TEST_F(SearchProviderTest, RemoveExtraAnswers) {

components/omnibox/search_provider.h

@@ -254,21 +254,35 @@ class SearchProvider : public BaseSearchProvider,
       const SearchSuggestionParser::NavigationResults& navigation_results,
       ACMatches* matches);
 
-  // Adds a match for each result in |results| to |map|. |is_keyword| indicates
-  // whether the results correspond to the keyword provider or default provider.
-  void AddHistoryResultsToMap(const HistoryResults& results,
-                              bool is_keyword,
-                              int did_not_accept_suggestion,
-                              MatchMap* map);
+  // Adds a match for each result in |raw_default_history_results_| or
+  // |raw_keyword_history_results_| to |map|. |is_keyword| indicates
+  // which one of the two.
+  void AddRawHistoryResultsToMap(bool is_keyword,
+                                 int did_not_accept_suggestion,
+                                 MatchMap* map);
+
+  // Adds a match for each transformed result in |results| to |map|.
+  void AddTransformedHistoryResultsToMap(
+      const SearchSuggestionParser::SuggestResults& results,
+      int did_not_accept_suggestion,
+      MatchMap* map);
 
   // Calculates relevance scores for all |results|.
-  SearchSuggestionParser::SuggestResults ScoreHistoryResults(
+  SearchSuggestionParser::SuggestResults ScoreHistoryResultsHelper(
       const HistoryResults& results,
       bool base_prevent_inline_autocomplete,
       bool input_multiple_words,
       const base::string16& input_text,
       bool is_keyword);
 
+  // Calculates relevance scores for |results|, adjusting for boundary
+  // conditions around multi-word queries. (See inline comments in function
+  // definition for more details.)
+  void ScoreHistoryResults(
+      const HistoryResults& results,
+      bool is_keyword,
+      SearchSuggestionParser::SuggestResults* scored_results);
+
   // Adds matches for |results| to |map|.
   void AddSuggestResultsToMap(
       const SearchSuggestionParser::SuggestResults& results,
@@ -321,9 +335,11 @@ class SearchProvider : public BaseSearchProvider,
   // Obtains a session token, regenerating if necessary.
   std::string GetSessionToken();
 
-  // Answers prefetch handling - finds previously displayed answer matching the
-  // current |input| and sets |prefetch_data_|.
-  void DoAnswersQuery(const AutocompleteInput& input);
+  // Answers prefetch handling - finds the previously displayed answer matching
+  // the current top-scoring history result. If there is a previous answer,
+  // returns the query data associated with it. Otherwise, returns an empty
+  // AnswersQueryData.
+  AnswersQueryData FindAnswersPrefetchData();
 
   // The amount of time to wait before sending a new suggest request after the
   // previous one.  Non-const because some unittests modify this value.
@@ -345,8 +361,13 @@ class SearchProvider : public BaseSearchProvider,
   AutocompleteInput keyword_input_;
 
   // Searches in the user's history that begin with the input text.
-  HistoryResults keyword_history_results_;
-  HistoryResults default_history_results_;
+  HistoryResults raw_keyword_history_results_;
+  HistoryResults raw_default_history_results_;
+
+  // Scored searches in the user's history - based on |keyword_history_results_|
+  // or |default_history_results_| as appropriate.
+  SearchSuggestionParser::SuggestResults transformed_keyword_history_results_;
+  SearchSuggestionParser::SuggestResults transformed_default_history_results_;
 
   // A timer to start a query to the suggest server after the user has stopped
   // typing for long enough.