Handle @proxy classes in type checker.

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 740 matching lines @@
       element.allSupertypesAndSelf = element.origin.allSupertypesAndSelf;
       // Stepwise assignment to ensure invariant.
       element.supertypeLoadState = STATE_STARTED;
       element.supertypeLoadState = STATE_DONE;
       element.resolutionState = STATE_DONE;
       // TODO(johnniwinther): Check matching type variables and
       // empty extends/implements clauses.
     }
     for (MetadataAnnotation metadata in element.metadata) {
       metadata.ensureResolved(compiler);
+      if (!element.isProxy && metadata.value == compiler.proxyConstant) {
+        element.isProxy = true;
+      }
     }
 
     // Force resolution of metadata on non-instance members since they may be
     // inspected by the backend while emitting. Metadata on instance members is
     // handled as a result of processing instantiated class members in the
     // enqueuer.
     // TODO(ahe): Avoid this eager resolution.
     element.forEachMember((_, Element member) {
       if (!member.isInstanceMember()) {
         compiler.withCurrentElement(member, () {
@@ skipping 3996 matching lines @@
     return finishConstructorReference(visit(expression),
                                       expression, expression);
   }
 }
 
 /// Looks up [name] in [scope] and unwraps the result.
 Element lookupInScope(Compiler compiler, Node node,
                       Scope scope, String name) {
   return Elements.unwrap(scope.lookup(name), compiler, node);
 }