dart2js: add compiler builtins to the core-runtime.

pkg/js_ast/lib/src/builder.dart

 // Copyright (c) 2013, 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.
 
 // Utilities for building JS ASTs at runtime.  Contains a builder class
 // and a parser that parses part of the language.
 
 part of js_ast;
 
 
@@ skipping 239 matching lines @@
     Template template = templateManager.lookupStatementTemplate(source);
     if (template == null) {
       MiniJsParser parser = new MiniJsParser(source);
       Statement statement = parser.statement();
       template = templateManager.defineStatementTemplate(source, statement);
     }
     return template;
   }
 
   /**
+   * Creates an Expression template for the given [source].
+   *
+   * The returned template is cached.
+   */
+  Template expressionTemplateFor(String source) {
+    return _findExpressionTemplate(source);
+  }
+
+  /**
    * Creates an Expression template without caching the result.
    */
   Template uncachedExpressionTemplate(String source) {
     MiniJsParser parser = new MiniJsParser(source);
     Expression expression = parser.expression();
     return new Template(
         source, expression, isExpression: true, forceCopy: false);
   }
 
   /**
@@ skipping 1062 matching lines @@
 
   Catch parseCatch() {
     expectCategory(LPAREN);
     Declaration errorName = parseVariableDeclaration();
     expectCategory(RPAREN);
     expectCategory(LBRACE);
     Block body = parseBlock();
     return new Catch(errorName, body);
   }
 }