Handle platform access through prefix in dart2dart

pkg/compiler/lib/src/dart_backend/placeholder_collector.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 dart_backend;
 
 class LocalPlaceholder {
   final String identifier;
   final Set<Node> nodes;
   LocalPlaceholder(this.identifier) : nodes = new Set<Node>();
@@ skipping 261 matching lines @@
         isNamedOptionalParameter()) {
       currentFunctionScope.registerParameter(node);
     } else if (Elements.isLocal(element) && !isTypedefParameter(element)) {
       makeLocalPlaceholder(node);
     }
   }
 
   void tryMakeMemberPlaceholder(Identifier node) {
     assert(node != null);
     if (node is Operator) return;
-    final identifier = node.source;
+    String identifier = node.source;
     if (fixedMemberNames.contains(identifier)) return;
     memberPlaceholders.putIfAbsent(
         identifier, () => new Set<Identifier>()).add(node);
   }
 
   void makeTypePlaceholder(Node node, DartType type) {
     Send send = node.asSend();
     if (send != null) {
       // Prefix.
       assert(send.receiver is Identifier);
@@ skipping 401 matching lines @@
 
   visitBlock(Block node) {
     for (Node statement in node.statements.nodes) {
       if (statement is VariableDefinitions) {
         makeVarDeclarationTypePlaceholder(statement);
       }
     }
     node.visitChildren(this);
   }
 }