Make await for cancel the stream when breaking out of the loop

runtime/vm/ast_printer.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/ast_printer.h"
 
 #include "vm/handles.h"
 #include "vm/log.h"
 #include "vm/object.h"
 #include "vm/os.h"
@@ skipping 394 matching lines @@
 
 
 void AstPrinter::VisitCatchClauseNode(CatchClauseNode* node) {
   VisitGenericAstNode(node);
 }
 
 
 void AstPrinter::VisitTryCatchNode(TryCatchNode* node) {
   ISL_Print("(%s ", node->PrettyName());
   node->try_block()->Visit(this);
-  if (node->catch_block() != NULL) {
-    node->catch_block()->Visit(this);
-  }
+  node->catch_block()->Visit(this);
   if (node->finally_block() != NULL) {
     ISL_Print("(finally ");
     node->finally_block()->Visit(this);
     ISL_Print(")");
   }
   ISL_Print(")");
 }
 
 
 void AstPrinter::VisitThrowNode(ThrowNode* node) {
@@ skipping 134 matching lines @@
   ASSERT(node_sequence != NULL);
   AstPrinter ast_printer;
   const char* function_name =
       parsed_function.function().ToFullyQualifiedCString();
   ISL_Print("Ast for function '%s' {\n", function_name);
   node_sequence->Visit(&ast_printer);
   ISL_Print("}\n");
 }
 
 }  // namespace dart