dart2js: Construct the entire output as a single AST before printing.

pkg/js_ast/lib/src/template.dart

 // Copyright (c) 2014, 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.
 
 part of js_ast;
 
 class TemplateManager {
   Map<String, Template> expressionTemplates = new Map<String, Template>();
   Map<String, Template> statementTemplates = new Map<String, Template>();
 
@@ skipping 41 matching lines @@
 
   // Null, unless there are named holes.
   List<String> holeNames;
   bool get isPositional => holeNames == null;
 
   Template(this.source, this.ast,
            {this.isExpression: true, this.forceCopy: false}) {
     _compile();
   }
 
-  Template.withExpressionResult(this.ast)
+  Template.withExpressionResult(this.ast, {hasPlaceholders : false})
       : source = null, isExpression = true, forceCopy = false {
     assert(ast is Expression);
-    assert(_checkNoPlaceholders());
-    positionalArgumentCount = 0;
-    instantiator = (arguments) => ast;
+    if (hasPlaceholders) {
+      _compile();
+    } else {
+      assert(_checkNoPlaceholders());
+      positionalArgumentCount = 0;
+      instantiator = (arguments) => ast;
+    }
   }
 
-  Template.withStatementResult(this.ast)
+  Template.withStatementResult(this.ast, {hasPlaceholders : false})
       : source = null, isExpression = false, forceCopy = false {
     assert(ast is Statement);
-    assert(_checkNoPlaceholders());
-    positionalArgumentCount = 0;
-    instantiator = (arguments) => ast;
+
+    if (hasPlaceholders) {
+      _compile();
+    } else {
+      assert(_checkNoPlaceholders());
+      positionalArgumentCount = 0;
+      instantiator = (arguments) => ast;
+    }
   }
 
   bool _checkNoPlaceholders() {
     InstantiatorGeneratorVisitor generator =
         new InstantiatorGeneratorVisitor(false);
     generator.compile(ast);
     return generator.analysis.count == 0;
   }
 
   void _compile() {
@@ skipping 659 matching lines @@
     if (count != before) containsInterpolatedNode.add(node);
     return null;
   }
 
   visitInterpolatedNode(InterpolatedNode node) {
     containsInterpolatedNode.add(node);
     if (node.isNamed) holeNames.add(node.nameOrPosition);
     ++count;
   }
 }