[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 980448b98868129f949124ac3467abcc36370eb8..da9a59f3de30923486ae96f5155b48b9c917696c 100644
--- a/components/autofill/core/browser/personal_data_manager.cc
+++ b/components/autofill/core/browser/personal_data_manager.cc
@@ -31,6 +31,7 @@
 #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/browser/account_tracker_service.h"
 #include "components/signin/core/common/signin_pref_names.h"
 #include "third_party/libaddressinput/src/cpp/include/libaddressinput/address_data.h"
@@ -796,15 +797,28 @@ std::vector<Suggestion> PersonalDataManager::GetProfileSuggestions(
       continue;
     base::string16 value_canon =
         AutofillProfile::CanonicalizeProfileString(value);
-    if (base::StartsWith(value_canon, field_contents_canon,
-                         base::CompareCase::SENSITIVE)) {
-      // Prefix match, add suggestion.
+    bool prefix_matched_suggestion = base::StartsWith(
+        value_canon, field_contents_canon, base::CompareCase::SENSITIVE);
+    if (prefix_matched_suggestion ||
+        FieldIsSuggestionSubstringStartingOnTokenBoundary(value, field_contents,
+                                                          false)) {
       matched_profiles.push_back(profile);
       suggestions.push_back(Suggestion(value));
       suggestions.back().backend_id = profile->guid();
+      suggestions.back().match = prefix_matched_suggestion
+                                     ? Suggestion::PREFIX_MATCH
+                                     : Suggestion::SUBSTRING_MATCH;
     }
   }
 
+  // Prefix matches should precede other token matches.
+  if (IsFeatureSubstringMatchEnabled()) {
+    std::stable_sort(suggestions.begin(), suggestions.end(),
+                     [](const Suggestion& a, const Suggestion& b) {
+                       return a.match < b.match;
+                     });
+  }
+
   // Don't show two suggestions if one is a subset of the other.
   std::vector<AutofillProfile*> unique_matched_profiles;
   std::vector<Suggestion> unique_suggestions;
@@ -856,6 +870,7 @@ std::vector<Suggestion> PersonalDataManager::GetCreditCardSuggestions(
     return std::vector<Suggestion>();
 
   std::list<const CreditCard*> cards_to_suggest;
+  std::list<const CreditCard*> substring_matched_cards;
   base::string16 field_contents_lower = base::i18n::ToLower(field_contents);
   for (const CreditCard* credit_card : GetCreditCards()) {
     // The value of the stored data for this field type in the |credit_card|.
@@ -878,12 +893,24 @@ std::vector<Suggestion> PersonalDataManager::GetCreditCardSuggestions(
            field_contents.size() >= 6)) {
         continue;
       }
-    } else if (!base::StartsWith(creditcard_field_lower, field_contents_lower,
-                                 base::CompareCase::SENSITIVE)) {
-      continue;
+      cards_to_suggest.push_back(credit_card);
+    } else if (base::StartsWith(creditcard_field_lower, field_contents_lower,
+                                base::CompareCase::SENSITIVE)) {
+      cards_to_suggest.push_back(credit_card);
+    } else if (FieldIsSuggestionSubstringStartingOnTokenBoundary(
+                   creditcard_field_lower, field_contents_lower, true)) {
+      substring_matched_cards.push_back(credit_card);
     }
+  }
 
-    cards_to_suggest.push_back(credit_card);
+  cards_to_suggest.sort(RankByMfu);
+
+  // Prefix matches should precede other token matches.
+  if (IsFeatureSubstringMatchEnabled()) {
+    substring_matched_cards.sort(RankByMfu);
+    cards_to_suggest.insert(cards_to_suggest.end(),
+                            substring_matched_cards.begin(),
+                            substring_matched_cards.end());
   }
 
   // De-dupe card suggestions. Full server cards shadow local cards, and
@@ -911,8 +938,6 @@ std::vector<Suggestion> PersonalDataManager::GetCreditCardSuggestions(
     }
   }
 
-  cards_to_suggest.sort(RankByMfu);
-
   std::vector<Suggestion> suggestions;
   for (const CreditCard* credit_card : cards_to_suggest) {
     // Make a new suggestion.