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

components/autofill/content/renderer/password_autofill_agent.h

 // 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.
 
 #ifndef COMPONENTS_AUTOFILL_CONTENT_RENDERER_PASSWORD_AUTOFILL_AGENT_H_
 #define COMPONENTS_AUTOFILL_CONTENT_RENDERER_PASSWORD_AUTOFILL_AGENT_H_
 
 #include <map>
 #include <vector>
 
@@ skipping 254 matching lines @@
   PasswordValueGatekeeper gatekeeper_;
 
   // True indicates that user debug information should be logged.
   bool logging_state_active_;
 
   // True indicates that the username field was autofilled, false otherwise.
   bool was_username_autofilled_;
   // True indicates that the password field was autofilled, false otherwise.
   bool was_password_autofilled_;
 
-  // Records original starting point of username element's selection range
-  // before preview.
-  int username_selection_start_;
+  // Records the username typed before suggestions preview.
+  base::string16 username_query_prefix_;
 
   // True indicates that all frames in a page have been rendered.
   bool did_stop_loading_;
 
   // Contains server predictions for username, password and/or new password
   // fields for individual forms.
   FormsPredictionsMap form_predictions_;
 
   base::WeakPtrFactory<PasswordAutofillAgent> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PasswordAutofillAgent);
 };
 
 }  // namespace autofill
 
 #endif  // COMPONENTS_AUTOFILL_CONTENT_RENDERER_PASSWORD_AUTOFILL_AGENT_H_