Reduce the number of captured variables in async code, by only capturing local

runtime/vm/ast_printer.cc

Index: runtime/vm/ast_printer.cc
diff --git a/runtime/vm/ast_printer.cc b/runtime/vm/ast_printer.cc
index 16b9468d6eb77071f2a9262f3d2ae2b4ded46c49..aa5c29f510c60af0979cf3de0b26a149aabb9d80 100644
--- a/runtime/vm/ast_printer.cc
+++ b/runtime/vm/ast_printer.cc
@@ -191,17 +191,22 @@ void AstPrinter::VisitAssignableNode(AssignableNode* node) {
 
 
 void AstPrinter::VisitAwaitNode(AwaitNode* node) {
-  VisitGenericAstNode(node);
+  ISL_Print("(*****%s***** (scope \"%p\") ", node->PrettyName(), node->scope());
+  node->VisitChildren(this);
+  ISL_Print(")");
 }
 
 
 void AstPrinter::VisitAwaitMarkerNode(AwaitMarkerNode* node) {
-  VisitGenericAstNode(node);
+  ISL_Print("(%s (async_scope \"%p\" await_scope \"%p\"))",
+            node->PrettyName(),
+            node->async_scope(),
+            node->await_scope());
 }
 
 
 void AstPrinter::VisitPrimaryNode(PrimaryNode* node) {
-  ISL_Print("*****%s***** \"%s\")",
+  ISL_Print("(*****%s***** \"%s\")",
             node->PrettyName(),
             node->primary().ToCString());
 }