A11y: Add/refactor methods for manipulating bitfields on AXNodeData.

ui/accessibility/tree_generator.cc

Index: ui/accessibility/tree_generator.cc
diff --git a/ui/accessibility/tree_generator.cc b/ui/accessibility/tree_generator.cc
index 480a040e921a4ef3eb121208ec865eda6d3af727..96bf0908bb0757a2b7ba0f7fbb79776bdab774e8 100644
--- a/ui/accessibility/tree_generator.cc
+++ b/ui/accessibility/tree_generator.cc
@@ -88,18 +88,18 @@ void TreeGenerator::BuildUniqueTreeWithSize(
   update.root_id = permuted[0];
   update.nodes.resize(node_count);
   update.nodes[0].id = permuted[0];
-  update.nodes[0].state = AX_STATE_NONE;
+  update.nodes[0].ClearBitfields();
   if (node_count > 1) {
     update.nodes[0].child_ids.push_back(permuted[1]);
     update.nodes[1].id = permuted[1];
-    update.nodes[1].state = AX_STATE_NONE;
+    update.nodes[1].ClearBitfields();
   }
 
   // The remaining nodes are assigned based on their parent
   // selected from the next bits from |tree_index|.
   for (int i = 2; i < node_count; ++i) {
     update.nodes[i].id = permuted[i];
-    update.nodes[i].state = AX_STATE_NONE;
+    update.nodes[i].ClearBitfields();
     int parent_index = (tree_index % i);
     tree_index /= i;
     update.nodes[parent_index].child_ids.push_back(permuted[i]);