Java: Implement clearsContent()

java/ql/src/semmle/code/java/dataflow/internal/DataFlowPrivate.qll

@@ -195,6 +195,15 @@ predicate readStep(Node node1, Content f, Node node2) {
   )
 }
 
+/**
+ * Holds if values stored inside content `c` are cleared at node `n`. For example,
+ * any value stored inside `f` is cleared at the pre-update node associated with `x`
+ * in `x.f = newValue`.
+ */
+predicate clearsContent(Node n, Content c) {
+  n = any(PostUpdateNode pun | storeStep(_, c, pun)).getPreUpdateNode()
+}
+
 /**
  * Gets a representative (boxed) type for `t` for the purpose of pruning
  * possible flow. A single type is used for all numeric types to account for