Get rid of AX_LINE_BREAKS attribute to improve performance.

content/browser/accessibility/browser_accessibility.cc

Index: content/browser/accessibility/browser_accessibility.cc
diff --git a/content/browser/accessibility/browser_accessibility.cc b/content/browser/accessibility/browser_accessibility.cc
index 0797a36a0fc0c8af0e8faa15f4e5189615321aa3..26e5b487c702235980102a9fe6f4e253e2b8f7b4 100644
--- a/content/browser/accessibility/browser_accessibility.cc
+++ b/content/browser/accessibility/browser_accessibility.cc
@@ -229,7 +229,7 @@ bool BrowserAccessibility::IsNextSiblingOnSameLine() const {
     const BrowserAccessibility* next_on_line =
         manager()->GetFromID(next_on_line_id);
     // In the case of a static text sibling, the object designated to be the
-    // next object on this line might be one of its children, i.e. the last
+    // next object on this line might be one of its children, i.e. the first
     // inline text box.
     return next_on_line && next_on_line->IsDescendantOf(next_sibling);
   }
@@ -533,9 +533,7 @@ int BrowserAccessibility::GetLineStartBoundary(
   DCHECK_LE(start, static_cast<int>(GetText().length()));
 
   if (IsSimpleTextControl()) {
-    const std::vector<int32_t>& line_breaks =
-        GetIntListAttribute(ui::AX_ATTR_LINE_BREAKS);
-    return ui::FindAccessibleTextBoundary(GetText(), line_breaks,
+    return ui::FindAccessibleTextBoundary(GetText(), GetLineStartOffsets(),
                                           ui::LINE_BOUNDARY, start, direction,
                                           affinity);
   }
@@ -1142,6 +1140,12 @@ std::string BrowserAccessibility::ComputeAccessibleNameFromDescendants() {
   return name;
 }
 
+std::vector<int> BrowserAccessibility::GetLineStartOffsets() const {
+  if (!instance_active())
+    return std::vector<int>();
+  return node()->GetOrComputeLineStartOffsets();
+}
+
 base::string16 BrowserAccessibility::GetInnerText() const {
   if (IsTextOnlyObject())
     return GetString16Attribute(ui::AX_ATTR_NAME);