[Autofill/Autocomplete Feature] Substring matching instead of prefix matching.

components/autofill/core/browser/personal_data_manager.cc

Index: components/autofill/core/browser/personal_data_manager.cc
diff --git a/components/autofill/core/browser/personal_data_manager.cc b/components/autofill/core/browser/personal_data_manager.cc
index 5441a475b7da657346d9603ce00b82bb4c6251dc..5391f9b79028c41f0acd7f23650b8bb552d95fae 100644
--- a/components/autofill/core/browser/personal_data_manager.cc
+++ b/components/autofill/core/browser/personal_data_manager.cc
@@ -29,6 +29,7 @@
 #include "components/autofill/core/browser/validation.h"
 #include "components/autofill/core/common/autofill_pref_names.h"
 #include "components/autofill/core/common/autofill_switches.h"
+#include "components/autofill/core/common/autofill_util.h"
 #include "components/signin/core/common/signin_pref_names.h"
 #include "third_party/libaddressinput/src/cpp/include/libaddressinput/address_data.h"
 #include "third_party/libaddressinput/src/cpp/include/libaddressinput/address_formatter.h"
@@ -229,6 +230,13 @@ bool RankByMfu(const AutofillDataModel* a, const AutofillDataModel* b) {
   return a->use_date() > b->use_date();
 }
 
+// Helper function to order prefix matched suggestions prior to substring
+// matched.
+bool OrderPrefixBeforeSubstring(const Suggestion& suggestion1,
+                                const Suggestion& suggestion2) {
+  return suggestion1.match < suggestion2.match;
+}
+
 }  // namespace
 
 PersonalDataManager::PersonalDataManager(const std::string& app_locale)
@@ -837,18 +845,29 @@ std::vector<Suggestion> PersonalDataManager::GetProfileSuggestions(
       if (values[i].empty())
         continue;
 
+      bool substring_token_matched = false;
       base::string16 value_canon =
           AutofillProfile::CanonicalizeProfileString(values[i]);
-      if (StartsWith(value_canon, field_contents_canon, true)) {
-        // Prefix match, add suggestion.
+      if (StartsWith(value_canon, field_contents_canon, true) ||
+          (substring_token_matched =
+               IsFeatureSubstringMatchEnabled() &&
+               IsContentsPrefixOfSuggestionToken(
+                   value_canon, field_contents_canon, CASE_SENSITIVE))) {
         matched_profiles.push_back(profile);
         suggestions.push_back(Suggestion(values[i]));
         suggestions.back().backend_id.guid = profile->guid();
         suggestions.back().backend_id.variant = i;
+        suggestions.back().match = substring_token_matched
+                                       ? Suggestion::SUBSTRING_MATCH
+                                       : Suggestion::PREFIX_MATCH;
       }
     }
   }
 
+  // Now sort profiles with prefix matched suggestions order before substring
+  // matched suggestions.
+  std::sort(suggestions.begin(), suggestions.end(), OrderPrefixBeforeSubstring);
+
   // Don't show two suggestions if one is a subset of the other.
   std::vector<AutofillProfile*> unique_matched_profiles;
   std::vector<Suggestion> unique_suggestions;