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

ui/accessibility/ax_tree_fuzzer.cc

Index: ui/accessibility/ax_tree_fuzzer.cc
diff --git a/ui/accessibility/ax_tree_fuzzer.cc b/ui/accessibility/ax_tree_fuzzer.cc
index de4b22d842d64ced1481678a5341fad54cb34c47..6369446b9043585c71b7f15c82703a7113e107f4 100644
--- a/ui/accessibility/ax_tree_fuzzer.cc
+++ b/ui/accessibility/ax_tree_fuzzer.cc
@@ -31,7 +31,7 @@ extern "C" int LLVMFuzzerTestOneInput(const unsigned char* data, size_t size) {
   while (i < size) {
     ui::AXNodeData node;
     node.id = data[i++];
-    node.state = 0;
+    node.ClearBitfields();
     if (i < size) {
       size_t child_count = data[i++];
       for (size_t j = 0; j < child_count && i < size; j++)