[fuzzy-app-search] Fix fuzzy app search issue

Increase the relevance threshold and use simple fuzzy app search instead
of weighted ratio to filter unwanted search results.

Bug: 1065455
Change-Id: I1c59368eb8dd3a235b2fd723098ac42cffca3aee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2143096Reviewed-by: Jia Meng <jiameng@chromium.org>
Commit-Queue: Thanh Nguyen <thanhdng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757768}

chrome/browser/ui/app_list/search/app_search_provider.cc

@@ -60,9 +60,9 @@ constexpr double kCrostiniTerminalRelevanceThreshold = 0.8;
 
 // Parameters for FuzzyTokenizedStringMatch.
 constexpr bool kUsePrefixOnly = false;
-constexpr bool kUseWeightedRatio = true;
+constexpr bool kUseWeightedRatio = false;
 constexpr bool kUseEditDistance = false;
-constexpr double kRelevanceThreshold = 0.3;
+constexpr double kRelevanceThreshold = 0.32;
 constexpr double kPartialMatchPenaltyRate = 0.9;
 
 // Adds |app_result| to |results| only in case no duplicate apps were already

chrome/browser/ui/app_list/search/tests/app_search_provider_unittest.cc

@@ -797,7 +797,7 @@ TEST_F(AppSearchProviderTest, FuzzyAppSearchTest) {
   feature_list.InitAndEnableFeature(app_list_features::kEnableFuzzyAppSearch);
   CreateSearch();
   EXPECT_EQ("Packaged App 1,Packaged App 2", RunQuery("pa"));
-  std::string result = RunQuery("packahe");
+  std::string result = RunQuery("ackaged");
   EXPECT_TRUE(result == "Packaged App 1,Packaged App 2" ||
               result == "Packaged App 2,Packaged App 1");
   EXPECT_EQ(kKeyboardShortcutHelperInternalName, RunQuery("Helper"));

chrome/common/string_matching/fuzzy_tokenized_string_match.cc

@@ -319,20 +319,10 @@ bool FuzzyTokenizedStringMatch::IsRelevant(const TokenizedString& query,
                  2;
   } else {
     // Use simple algorithm to calculate match ratio.
-    double partial_match = 0.0;
-    for (const auto& query_token : query.tokens()) {
-      for (const auto& text_token : text.tokens()) {
-        partial_match =
-            std::max(partial_match,
-                     SequenceMatcher(query_token, text_token, use_edit_distance)
-                         .Ratio());
-      }
-    }
-    const double partial_scale = 0.9;
     relevance_ =
-        (std::max(
-             SequenceMatcher(query_text, text_text, use_edit_distance).Ratio(),
-             partial_match * partial_scale) +
+        (SequenceMatcher(base::i18n::ToLower(query_text),
+                         base::i18n::ToLower(text_text), use_edit_distance)
+             .Ratio() +
          prefix_score) /
         2;
   }