Add support for setting password value gated on user's gesture in a page

public/web/WebAutofillClient.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 35 matching lines @@
 public:
     // Informs the browser an interactive autocomplete has been requested.
     virtual void didRequestAutocomplete(const WebFormElement&, const WebAutocompleteParams&) { }
 
     // These methods are called when the users edits a text-field.
     virtual void textFieldDidEndEditing(const WebInputElement&) { }
     virtual void textFieldDidChange(const WebFormControlElement&) { }
     virtual void textFieldDidReceiveKeyDown(const WebInputElement&, const WebKeyboardEvent&) { }
     // This is called when a datalist indicator is clicked.
     virtual void openTextDataListChooser(const WebInputElement&) { }
+    // Called the first time the user interacts with the page after a load.
+    virtual void firstUserGestureObserved() { }
 
     // Informs the client whether or not any subsequent text changes should be ignored.
     virtual void setIgnoreTextChanges(bool ignore) { }
 
     virtual void didAssociateFormControls(const WebVector<WebNode>&) { }
 
 protected:
     virtual ~WebAutofillClient() { }
 };
 
 } // namespace blink
 
 #endif