Add fallback to load the original version of dart:io library

runtime/bin/gen_snapshot.cc

 // Copyright (c) 2013, 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.
 
 // Generate a snapshot file after loading all the scripts specified on the
 // command line.
 
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
@@ skipping 287 matching lines @@
 
   Dart_Handle resolved_url = url;
   if (mapped_url_string != NULL) {
     // Mapped urls are relative to working directory.
     resolved_url = ResolveScriptUri(mapped_url_string);
     if (Dart_IsError(resolved_url)) {
       return resolved_url;
     }
   }
 
+  if (DartUtils::IsDartIOLibURL(url_string)) {
+    // No url mapping for dart:io. Load original version.
+    return Builtin::LoadAndCheckLibrary(Builtin::kIOLibrary);
+  }

[siva, 2013/04/19 17:47:50]

Not sure if I understand this. The comment states that if not url mapping for
dart:io. Load original version but it seems like the original version will be
loaded even when mapped_url_string is non NULL, could you elaborate a bit more.

[podivilov, 2013/04/20 07:34:22]

Good spot! I misinterpreted "return resolved_url" above.

+
   // Get the file path out of the url.
   Dart_Handle file_path = FilePathFromUri(
       DartUtils::GetStringValue(resolved_url));
   if (Dart_IsError(file_path)) {
     return file_path;
   }
 
   return DartUtils::LoadSource(NULL,
                                library,
                                url,
@@ skipping 203 matching lines @@
     CreateAndWriteSnapshot();
 
     Dart_EnterIsolate(UriResolverIsolateScope::isolate);
     Dart_ShutdownIsolate();
   } else {
     SetupForGenericSnapshotCreation();
     CreateAndWriteSnapshot();
   }
   return 0;
 }