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

ash/system/user/button_from_view.cc

Index: ash/system/user/button_from_view.cc
diff --git a/ash/system/user/button_from_view.cc b/ash/system/user/button_from_view.cc
index 0772fc2d5d4d64defc41021e3b68cb5249656f23..6bd8fbd027060fbd8ecab2c2058ab7b3a54e5b6f 100644
--- a/ash/system/user/button_from_view.cc
+++ b/ash/system/user/button_from_view.cc
@@ -79,6 +79,7 @@ void ButtonFromView::GetAccessibleNodeData(ui::AXNodeData* node_data) {
   // use the content's label.
   if (node_data->GetStringAttribute(ui::AX_ATTR_NAME).empty()) {
     ui::AXNodeData content_data;
+    content_data.ClearBitfields();
     content_->GetAccessibleNodeData(&content_data);
     node_data->SetName(content_data.GetStringAttribute(ui::AX_ATTR_NAME));
   }