Use text affinity to return correct accessible line boundaries.

third_party/WebKit/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 301 matching lines @@
 // because on some platforms this determines how the accessible description
 // is exposed.
 enum WebAXDescriptionFrom {
     WebAXDescriptionFromUninitialized = -1,
     WebAXDescriptionFromAttribute = 0,
     WebAXDescriptionFromContents,
     WebAXDescriptionFromPlaceholder,
     WebAXDescriptionFromRelatedElement,
 };
 
+// Text affinity for the start or end of a selection.
+enum WebAXTextAffinity {
+    WebAXTextAffinityUpstream,
+    WebAXTextAffinityDownstream
+};
+
 } // namespace blink
 
 #endif