Get rid of AX_LINE_BREAKS attribute to improve performance.

ui/accessibility/ax_enums.idl

 // Copyright 2014 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.
 
 // TODO(nektar): Migrate entire file to Mojoq.
 // These should be kept in sync with third_party/WebKit/public/web/WebAXEnums.h
 // until the Chromium and Blink trees are merged.
 [camel_case_enum_to_string=true] namespace ui {
 
   // For new entries to the following three enums, also add to
@@ skipping 372 matching lines @@
     // a table cell is a child of a row, and an 'indirect' child of a
     // column.
     indirect_child_ids,
 
     // Relationships between this element and other elements.
     controls_ids,
     describedby_ids,
     flowto_ids,
     labelledby_ids,
 
-    // For static text. Character indices where line breaks occur.
-    line_breaks,
-
     // For static text. These int lists must be the same size; they represent
     // the start and end character offset of each marker. Examples of markers
     // include spelling and grammar errors, and find-in-page matches.
     marker_types,
     marker_starts,
     marker_ends,
 
     // For a table, the cell ids in row-major order, with duplicate entries
     // when there's a rowspan or colspan, and with -1 for missing cells.
     // There are always exactly rows * columns entries.
     cell_ids,
 
     // For a table, the unique cell ids in row-major order of their first
     // occurrence.
     unique_cell_ids,
 
     // For inline text. This is the pixel position of the end of this
     // character within the bounding rectangle of this object, in the
     // direction given by AX_ATTR_TEXT_DIRECTION. For example, for left-to-right
     // text, the first offset is the right coordinate of the first character
     // within the object's bounds, the second offset is the right coordinate
     // of the second character, and so on.
     character_offsets,
+    
+    // Used for caching. Do not read directly. Use |AXNode::GetLineStartOffsets|
+    // For all objects with text content. A list of the start offset of each
+    // line of text inside this object.
+    line_starts,

[dmazzoni, 2016/09/13 17:29:38]

Maybe it'd be more clear to call it cached_line_starts?

 
     // For inline text. These int lists must be the same size; they represent
     // the start and end character offset of each word within this text.
     word_starts,
     word_ends
   };
 
   enum AXMarkerType {
     // Assignments are ignored by the parser, but are kept here for clarity.
     spelling = 1,
@@ skipping 109 matching lines @@
     // First node is before the second one.
     before,
 
     // Nodes are the same.
     equal,
 
     // First node is after the second one.
     after
   };
 };