JS: add SourceNode support for chained method calls

javascript/ql/src/semmle/javascript/dataflow/Sources.qll

@@ -131,6 +131,26 @@ abstract class SourceNode extends DataFlow::Node {
     )
   }
 
+  /**
+   * Gets a method call that invokes a method on this node.
+   *
+   * This includes only calls that have the syntactic shape of a method call,
+   * that is, `o.m(...)` or `o[p](...)`.
+   */
+  DataFlow::CallNode getAMethodCall() {
+    result = getAMethodCall(_)
+  }
+
+  /**
+   * Gets a chained method call that invokes `methodName` last.
+   *
+   * The chain steps include only calls that have the syntactic shape of a method call,
+   * that is, `o.m(...)` or `o[p](...)`.
+   */
+  DataFlow::CallNode getAChainedMethodCall(string methodName) {
+    result = getAMethodCall*().getAMethodCall(methodName)
+  }
+
   /**
    * Gets a `new` call that invokes constructor `constructorName` on this node.
    */