Add a compile time error for non-static const fields

sdk/lib/_internal/compiler/implementation/resolution/members.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 resolution;
 
 abstract class TreeElements {
   Element get currentElement;
   Setlet<Node> get superUses;
 
@@ skipping 960 matching lines @@
             compiler.reportError(
                 member,
                 MessageKind.ILLEGAL_CONSTRUCTOR_MODIFIERS,
                 {'modifiers': mismatchedFlags});
           }
           if (member.modifiers.isConst) {
             constConstructors.add(member);
           }
         }
         if (member.isField) {
-          if (!member.modifiers.isStatic &&
-              !member.modifiers.isFinal) {
+          if (member.modifiers.isConst && !member.modifiers.isStatic) {
+            compiler.reportError(
+                member, MessageKind.ILLEGAL_CONST_FIELD_MODIFIER);
+          }
+          if (!member.modifiers.isStatic && !member.modifiers.isFinal) {
             nonFinalInstanceFields.add(member);
           }
         }
         checkAbstractField(member);
         checkUserDefinableOperator(member);
       });
     });
     if (!constConstructors.isEmpty && !nonFinalInstanceFields.isEmpty) {
       Spannable span = constConstructors.length > 1
           ? cls : constConstructors[0];
@@ skipping 3699 matching lines @@
   TreeElements _treeElements;
 
   bool get hasTreeElements => _treeElements != null;
 
   TreeElements get treeElements {
     assert(invariant(this, _treeElements !=null,
         message: "TreeElements have not been computed for $this."));
     return _treeElements;
   }
 }