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

components/pdf/renderer/pdf_accessibility_tree.cc

Index: components/pdf/renderer/pdf_accessibility_tree.cc
diff --git a/components/pdf/renderer/pdf_accessibility_tree.cc b/components/pdf/renderer/pdf_accessibility_tree.cc
index d4c225784253cde2bbde6fd17b8dddfdc08abcbf..6799240f4d7579db9c061a545be9e1fd5aa55972 100644
--- a/components/pdf/renderer/pdf_accessibility_tree.cc
+++ b/components/pdf/renderer/pdf_accessibility_tree.cc
@@ -273,9 +273,10 @@ ui::AXNodeData* PdfAccessibilityTree::CreateNode(ui::AXRole role) {
   DCHECK(render_accessibility);
 
   ui::AXNodeData* node = new ui::AXNodeData();
+  node->ClearBitfields();
   node->id = render_accessibility->GenerateAXID();
   node->role = role;
-  node->state = 1 << ui::AX_STATE_READ_ONLY;
+  node->AddState(ui::AX_STATE_READ_ONLY);
 
   // All nodes other than the first one have coordinates relative to
   // the first node.