Fix warnings in dart2js.

sdk/lib/_internal/compiler/implementation/patch_parser.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.
 
 /**
  * This library contains the infrastructure to parse and integrate patch files.
  *
  * Three types of elements can be patched: [LibraryElement], [ClassElement],
  * [FunctionElement]. Patches are introduced in patch libraries which are loaded
  * together with the corresponding origin library. Which libraries that are
@@ skipping 160 matching lines @@
                                    imports);
       new PatchParser(patchListener).parseUnit(tokens);
     });
   }
 
   void parsePatchClassNode(PartialClassElement element) {
     // Parse [PartialClassElement] using a "patch"-aware parser instead
     // of calling its [parseNode] method.
     if (element.cachedNode != null) return;
 
-    return measure(() => compiler.withCurrentElement(element, () {
+    measure(() => compiler.withCurrentElement(element, () {
       PatchMemberListener listener = new PatchMemberListener(compiler, element);
       Parser parser = new PatchClassElementParser(listener);
       Token token = parser.parseTopLevelDeclaration(element.beginToken);
       assert(identical(token, element.endToken.next));
       element.cachedNode = listener.popNode();
       assert(listener.nodes.isEmpty);
 
       Link<Element> patches = element.localMembers;
       applyContainerPatch(element.origin, patches);
     }));
@@ skipping 357 matching lines @@
 
 // TODO(johnniwinther): Add unittest when patch is (real) metadata.
 bool isPatchElement(Element element) {
   // TODO(lrn): More checks needed if we introduce metadata for real.
   // In that case, it must have the identifier "native" as metadata.
   for (Link link = element.metadata; !link.isEmpty; link = link.tail) {
     if (link.head is PatchMetadataAnnotation) return true;
   }
   return false;
 }