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

runtime/bin/gen_snapshot.cc

Index: runtime/bin/gen_snapshot.cc
diff --git a/runtime/bin/gen_snapshot.cc b/runtime/bin/gen_snapshot.cc
index ea6911918fcbd4ff9397771ea59ef55ce7075eb2..2880913471844e45e0e0b738340b54538b4f0d1a 100644
--- a/runtime/bin/gen_snapshot.cc
+++ b/runtime/bin/gen_snapshot.cc
@@ -305,6 +305,11 @@ static Dart_Handle CreateSnapshotLibraryTagHandler(Dart_LibraryTag tag,
     }
   }
 
+  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));