Get rid of AX_LINE_BREAKS attribute to improve performance.

ui/accessibility/ax_node.cc

 // 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.
 
 #include "ui/accessibility/ax_node.h"
+
+#include <algorithm>
+
+#include "base/strings/string16.h"
 #include "ui/gfx/transform.h"
 
 namespace ui {
 
 AXNode::AXNode(AXNode* parent, int32_t id, int32_t index_in_parent)
     : index_in_parent_(index_in_parent), parent_(parent) {
   data_.id = id;
 }
 
 AXNode::~AXNode() {
@@ skipping 28 matching lines @@
 
 bool AXNode::IsDescendantOf(AXNode* ancestor) {
   if (this == ancestor)
     return true;
   else if (parent())
     return parent()->IsDescendantOf(ancestor);
 
   return false;
 }
 
+std::vector<int> AXNode::GetOrComputeLineStartOffsets() {
+  std::vector<int> line_offsets;
+  if (data().GetIntListAttribute(ui::AX_ATTR_LINE_STARTS, &line_offsets))
+    return line_offsets;
+
+  int end_offset;
+  ComputeLineStartOffsets(&line_offsets, &end_offset);
+  data_.AddIntListAttribute(ui::AX_ATTR_LINE_STARTS, line_offsets);
+  return line_offsets;
+}
+
+void AXNode::ComputeLineStartOffsets(std::vector<int>* line_offsets,
+                                     int* end_offset) const {

[David Tseng, 2016/09/13 17:41:27]

Is this meant to work on any node (e.g.
<div aria-label="hello"></div>
)?

What does line start offsets mean?

+  DCHECK(line_offsets);
+  DCHECK(end_offset);
+  for (const AXNode* child : children()) {
+    DCHECK(child);
+    if (child->child_count()) {
+      child->ComputeLineStartOffsets(line_offsets, end_offset);
+      continue;
+    }
+
+    base::string16 text = child->data().GetString16Attribute(ui::AX_ATTR_NAME);
+    *end_offset += static_cast<int>(text.length());

[David Tseng, 2016/09/13 17:41:27]

Just make end_offset a size_t

+    if (!child->data().HasIntAttribute(ui::AX_ATTR_NEXT_ON_LINE_ID))
+      line_offsets->push_back(*end_offset);
+  }
+}
+
 }  // namespace ui