[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 82167f9bfa2e6fce90a9c5c1fc186a68238e514d..dc68cc021dc1834647d14ad02f806e07e6374050 100644
--- a/components/autofill/core/browser/personal_data_manager.cc
+++ b/components/autofill/core/browser/personal_data_manager.cc
@@ -30,6 +30,7 @@
 #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"
@@ -760,6 +761,7 @@ const std::vector<CreditCard*>& PersonalDataManager::GetCreditCards() const {
     credit_cards_.insert(credit_cards_.end(), server_credit_cards_.begin(),
                          server_credit_cards_.end());
   }
+
   return credit_cards_;
 }
 
@@ -792,14 +794,32 @@ std::vector<Suggestion> PersonalDataManager::GetProfileSuggestions(
       continue;
     base::string16 value_canon =
         AutofillProfile::CanonicalizeProfileString(value);
-    if (StartsWith(value_canon, field_contents_canon, true)) {
-      // Prefix match, add suggestion.
+    // CanonicalizeProfileString() returns lower-case string with all
+    // separator substituted by whitespaces and trims off trailing whitespace
+    // if any. Passing |value_canon| and |field_contents_canon| to
+    // ContainsTokenThatStartsWith() may lead to unexpected result, hence
+    // preferred passing |values[i]| and |field_contents| instead.
+    bool substring_matched_suggestion = false;
+    if (StartsWith(value_canon, field_contents_canon, true) ||
+        (substring_matched_suggestion =
+             ContainsTokenThatStartsWith(value, field_contents, false))) {
       matched_profiles.push_back(profile);
       suggestions.push_back(Suggestion(value));
       suggestions.back().backend_id = profile->guid();
+      suggestions.back().match = substring_matched_suggestion
+                                     ? Suggestion::SUBSTRING_MATCH
+                                     : Suggestion::PREFIX_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;
@@ -848,6 +868,7 @@ std::vector<Suggestion> PersonalDataManager::GetCreditCardSuggestions(
     const AutofillType& type,
     const base::string16& field_contents) {
   std::list<const CreditCard*> cards_to_suggest;
+  std::list<const CreditCard*> substring_matched_suggestions;
   for (const CreditCard* credit_card : GetCreditCards()) {
     // The value of the stored data for this field type in the |credit_card|.
     base::string16 creditcard_field_value =
@@ -866,11 +887,23 @@ std::vector<Suggestion> PersonalDataManager::GetCreditCardSuggestions(
            field_contents.size() >= 6)) {
         continue;
       }
-    } else if (!StartsWith(creditcard_field_value, field_contents, false)) {
-      continue;
+      cards_to_suggest.push_back(credit_card);
+    } else if (StartsWith(creditcard_field_value, field_contents, false)) {
+      cards_to_suggest.push_back(credit_card);
+    } else if (ContainsTokenThatStartsWith(creditcard_field_value,
+                                           field_contents, false)) {
+      substring_matched_suggestions.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_suggestions.sort(RankByMfu);
+    cards_to_suggest.insert(cards_to_suggest.end(),
+                            substring_matched_suggestions.begin(),
+                            substring_matched_suggestions.end());
   }
 
   // De-dupe card suggestions. Full server cards shadow local cards, and
@@ -898,8 +931,6 @@ 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.