Do not always error-out when evaluating a map that is not a compile time constant.

sdk/lib/_internal/compiler/implementation/compile_time_constants.dart

 // Copyright (c) 2012, 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 dart2js;
 
 /**
  * The [ConstantHandler] keeps track of compile-time constants,
  * initializations of global and static fields, and default values of
  * optional parameters.
@@ skipping 283 matching lines @@
     }
     // TODO(floitsch): get type parameters.
     DartType type = new InterfaceType(compiler.listClass);
     Constant constant = new ListConstant(type, arguments);
     compiler.constantHandler.registerCompileTimeConstant(constant);
     return constant;
   }
 
   Constant visitLiteralMap(LiteralMap node) {
     if (!node.isConst()) {
-      signalNotCompileTimeConstant(node);
-      error(node);
+      return signalNotCompileTimeConstant(node);
     }
     List<StringConstant> keys = <StringConstant>[];
     Map<StringConstant, Constant> map = new Map<StringConstant, Constant>();
     for (Link<Node> link = node.entries.nodes;
          !link.isEmpty;
          link = link.tail) {
       LiteralMapEntry entry = link.head;
       Constant key = evaluateConstant(entry.key);
       if (!key.isString() || entry.key.asStringNode() == null) {
         MessageKind kind = MessageKind.KEY_NOT_A_STRING_LITERAL;
@@ skipping 494 matching lines @@
             // Use the default value.
             fieldValue = compiler.compileConstant(field);
           }
           jsNewArguments.add(fieldValue);
         },
         includeBackendMembers: true,
         includeSuperMembers: true);
     return jsNewArguments;
   }
 }