First step toward fixing cascades (issue 5062)

compiler/java/com/google/dart/compiler/ast/ASTVisitor.java

Index: compiler/java/com/google/dart/compiler/ast/ASTVisitor.java
===================================================================
--- compiler/java/com/google/dart/compiler/ast/ASTVisitor.java	(revision 12980)
+++ compiler/java/com/google/dart/compiler/ast/ASTVisitor.java	(working copy)
@@ -137,6 +137,10 @@
     return visitInvocation(node);
   }
 
+  public R visitCascadeExpression(DartCascadeExpression node) {
+    return visitExpression(node);
+  }
+
   public R visitCase(DartCase node) {
     return visitSwitchMember(node);
   }