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

components/autofill/core/browser/autocomplete_history_manager.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/autofill/core/browser/autocomplete_history_manager.h"
 
 #include <vector>
 
 #include "base/prefs/pref_service.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/strings/string16.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/autofill/core/browser/autofill_client.h"
 #include "components/autofill/core/browser/autofill_driver.h"
 #include "components/autofill/core/browser/autofill_external_delegate.h"
 #include "components/autofill/core/browser/validation.h"
 #include "components/autofill/core/common/autofill_pref_names.h"
+#include "components/autofill/core/common/autofill_util.h"
 #include "components/autofill/core/common/form_data.h"
 
 namespace autofill {
 namespace {
 
 // Limit on the number of suggestions to appear in the pop-up menu under an
 // text input element in a form.
 const int kMaxAutocompleteMenuItems = 6;
 
 bool IsTextField(const FormFieldData& field) {
@@ skipping 46 matching lines @@
   // See http://crbug.com/68783.
   if (!result) {
     SendSuggestions(NULL);
     return;
   }
 
   DCHECK_EQ(AUTOFILL_VALUE_RESULT, result->GetType());
   const WDResult<std::vector<base::string16> >* autofill_result =
       static_cast<const WDResult<std::vector<base::string16> >*>(result);
   std::vector<base::string16> suggestions = autofill_result->GetValue();
-  SendSuggestions(&suggestions);
+
+  if (!IsFeatureSubstringMatchEnabled() || user_input_.empty()) {
+    SendSuggestions(&suggestions);
+  } else {
+    std::vector<base::string16> preferred_suggestions;
+    for (base::string16 suggestion : suggestions) {
+      if (StartsWith(suggestion, user_input_, false) ||
+          IsContentsPrefixOfSuggestionToken(suggestion, user_input_, false)) {
+        preferred_suggestions.push_back(suggestion);
+      }
+    }
+
+    SendSuggestions(&preferred_suggestions);
+  }
 }
 
 void AutocompleteHistoryManager::OnGetAutocompleteSuggestions(
     int query_id,
     const base::string16& name,
     const base::string16& prefix,
     const std::string& form_control_type,
     const std::vector<Suggestion>& suggestions) {
   CancelPendingQuery();
 
   query_id_ = query_id;
   autofill_suggestions_ = suggestions;
   if (!autofill_client_->IsAutocompleteEnabled() ||
       form_control_type == "textarea") {
     SendSuggestions(NULL);
     return;
   }
 
   if (database_.get()) {
+    user_input_ = prefix;
     pending_query_handle_ = database_->GetFormValuesForElementName(
-        name, prefix, kMaxAutocompleteMenuItems, this);
+        name, IsFeatureSubstringMatchEnabled() ? base::string16() : prefix,
+        kMaxAutocompleteMenuItems, this);
   }
 }
 
 void AutocompleteHistoryManager::OnFormSubmitted(const FormData& form) {
   if (!autofill_client_->IsAutocompleteEnabled())
     return;
 
   if (driver_->IsOffTheRecord())
     return;
 
@@ skipping 64 matching lines @@
     }
   }
 
   external_delegate_->OnSuggestionsReturned(query_id_, autofill_suggestions_);
 
   query_id_ = 0;
   autofill_suggestions_.clear();
 }
 
 }  // namespace autofill