Enable print forwarding.

Source/WebCore/bindings/dart/DartController.cpp

 // Copyright (c) 2009, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 117 matching lines @@
 
     Dart_Handle web_sql = Dart_LookupLibrary(Dart_NewStringFromCString("dart:web_sql"));
     ASSERT(!Dart_IsError(web_sql));
     Dart_SetNativeResolver(web_sql, web_sqlSnapshotResolver);
 
     // Import html library into core to make it all available to the user directly.
     Dart_Handle core = Dart_LookupLibrary(Dart_NewStringFromCString("dart:core"));
     Dart_LibraryImportLibrary(core, html, Dart_Null());
 
     // Setup configuration closures
-    copyValue(html, "_printClosure", "dart:core", 0, "_printClosure");
+    copyValue(html, getenv("DART_FORWARDING_PRINT") ? "_forwardingPrintClosure" : "_printClosure", "dart:core", 0, "_printClosure");
     copyValue(html, "_timerFactoryClosure", "dart:async", "_TimerFactory", "_factory");
 
     if (isDOMEnabled) {
         // Create strongly reachable document wrapper. Document wrapper acts as a
         // retainer for in-document node wrappers group. There is no need to destroy
         // this persistent handle explicitly because we will shutdown the isolate on
         // navigation.
         domData->setDocumentWrapper(Dart_NewPersistentHandle(DartDocument::toDart(document)));
 
         DartDebugServer::shared().registerIsolate(isolate);
@@ skipping 553 matching lines @@
 }
 
 DartController* DartController::retrieve(ScriptExecutionContext* context)
 {
     if (!context || !context->isDocument())
         return 0;
     return retrieve(static_cast<Document*>(context)->frame());
 }
 
 }