Support html br element in AX Tree.

public/web/WebAXEnums.h

 /*
  * Copyright (C) 2013 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 167 matching lines @@
     WebAXRoleTextField,
     WebAXRoleTime,
     WebAXRoleTimer,
     WebAXRoleToggleButton,
     WebAXRoleToolbar,
     WebAXRoleTreeGrid,
     WebAXRoleTreeItem,
     WebAXRoleTree,
     WebAXRoleUserInterfaceTooltip,
     WebAXRoleWebArea,
+    WebAXRoleLineBreak,
     WebAXRoleWindow,
 };
 
 // Accessibility states, used as a bitmask.
 enum WebAXState {
     WebAXStateBusy,
     WebAXStateChecked,
     WebAXStateEnabled,
     WebAXStateExpanded,
     WebAXStateFocusable,
@@ skipping 56 matching lines @@
     WebAXInvalidStateFalse,
     WebAXInvalidStateTrue,
     WebAXInvalidStateSpelling,
     WebAXInvalidStateGrammar,
     WebAXInvalidStateOther
 };
 
 } // namespace blink
 
 #endif