Views a11y: Add comment to explain usage of AXNodeData's |state| member.

ui/accessibility/ax_node_data.cc

Index: ui/accessibility/ax_node_data.cc
diff --git a/ui/accessibility/ax_node_data.cc b/ui/accessibility/ax_node_data.cc
index 66deec361b660a098663da34a9a7490dbd7b4af4..8f8706073dc2deec7acfdbdd038f055b3100baf4 100644
--- a/ui/accessibility/ax_node_data.cc
+++ b/ui/accessibility/ax_node_data.cc
@@ -60,6 +60,8 @@ typename std::vector<std::pair<FirstType, SecondType>>::const_iterator
 AXNodeData::AXNodeData()
     : id(-1),
       role(AX_ROLE_UNKNOWN),
+      // Turn on all flags to more easily catch bugs where no flags are set.
+      // This will be cleared back to a 0-state before use.
       state(0xFFFFFFFF),
       offset_container_id(-1) {
 }