Allow use of deferred type-literals in non-constant contexts.

pkg/compiler/lib/src/js_backend/constant_handler_javascript.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_backend;
 
 /// [ConstantCompilerTask] for compilation of constants for the JavaScript
 /// backend.
 ///
 /// Since this task needs to distinguish between frontend and backend constants
@@ skipping 23 matching lines @@
       return result;
     });
   }
 
   void compileVariable(VariableElement element) {
     measure(() {
       jsConstantCompiler.compileVariable(element);
     });
   }
 
-  ConstantExpression compileNode(Node node, TreeElements elements) {
+  ConstantExpression compileNode(Node node, TreeElements elements,
+                                 {bool enforceConst: true}) {
     return measure(() {
       ConstantExpression result =
-          dartConstantCompiler.compileNode(node, elements);
-      jsConstantCompiler.compileNode(node, elements);
+          dartConstantCompiler.compileNode(node, elements,
+                                           enforceConst: enforceConst);
+      jsConstantCompiler.compileNode(node, elements,
+          enforceConst: enforceConst);
       return result;
     });
   }
 
   ConstantExpression compileMetadata(MetadataAnnotation metadata,
                            Node node,
                            TreeElements elements) {
     return measure(() {
       ConstantExpression constant =
           dartConstantCompiler.compileMetadata(metadata, node, elements);
@@ skipping 97 matching lines @@
 
   ConstantExpression getInitialValueFor(VariableElement element) {
     ConstantExpression initialValue =
         initialVariableValues[element.declaration];
     if (initialValue == null) {
       compiler.internalError(element, "No initial value for given element.");
     }
     return initialValue;
   }
 
-  ConstantExpression compileNode(Node node, TreeElements elements) {
-    return compileNodeWithDefinitions(node, elements);
+  ConstantExpression compileNode(Node node, TreeElements elements,
+                                 {bool enforceConst: true}) {
+    return compileNodeWithDefinitions(node, elements, isConst: enforceConst);
   }
 
   ConstantExpression compileNodeWithDefinitions(Node node,
                                       TreeElements definitions,
                                       {bool isConst: true}) {
     ConstantExpression constant = nodeConstantMap[node];
     if (constant != null) {
       return constant;
     }
     constant =
@@ skipping 76 matching lines @@
     // TODO(ahe): This doesn't belong here. Rename this class and generalize.
     var closureClassMap =
         constants.compiler.closureToClassMapper.closureMappingCache
         .remove(node);
     if (closureClassMap != null) {
       closureClassMap.removeMyselfFrom(
           constants.compiler.enqueuer.codegen.universe);
     }
   }
 }