Use correct position when setting pos_in_set for tabs.

ui/accessibility/ax_node_data.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_data.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <set>
@@ skipping 351 matching lines @@
 void AXNodeData::AddStringAttribute(
     AXStringAttribute attribute, const std::string& value) {
   string_attributes.push_back(std::make_pair(attribute, value));
 }
 
 void AXNodeData::AddIntAttribute(
     AXIntAttribute attribute, int value) {
   int_attributes.push_back(std::make_pair(attribute, value));
 }
 
+void AXNodeData::AddValidatedIntAttribute(AXValidatedIntAttribute attribute,
+                                          int value) {
+  switch (attribute) {
+    case ui::AX_ATTR_INDEX_IN_SET:
+      if (value < 0) {
+        NOTREACHED();
+        return;
+      }
+      AddIntAttribute(ui::AX_ATTR_POS_IN_SET, value + 1);
+      break;
+    default:
+      NOTREACHED();
+  }
+}
+
 void AXNodeData::AddFloatAttribute(
     AXFloatAttribute attribute, float value) {
   float_attributes.push_back(std::make_pair(attribute, value));
 }
 
 void AXNodeData::AddBoolAttribute(
     AXBoolAttribute attribute, bool value) {
   bool_attributes.push_back(std::make_pair(attribute, value));
 }
 
@@ skipping 539 matching lines @@
     }
   }
 
   if (!child_ids.empty())
     result += " child_ids=" + IntVectorToString(child_ids);
 
   return result;
 }
 
 }  // namespace ui