Introduce (private) ZLibFilter to dart:io.

runtime/bin/common.dart

Index: runtime/bin/common.dart
diff --git a/runtime/bin/common.dart b/runtime/bin/common.dart
index 33ce2a5dd9ef2e933205cefb6f3f973506935555..0455397e41092db060578105e05c764cd3dc30d1 100644
--- a/runtime/bin/common.dart
+++ b/runtime/bin/common.dart
@@ -54,6 +54,21 @@ class OSError {
   final int errorCode;
 }
 
+/**
+ * An [InternalError] can be thrown from native calls when an error occours
+ * inside native code.
+ */
+class InternalError {
+  const InternalError([String this.message = ""]);
+
+  String toString() {
+    if (message.isEmpty) return "InternalError";
+    return "InternalError: $message";
+  }
+
+  final String message;
+}
+
 
 // Check if a List is a builtin VM List type. Returns true
 // if the List is a builtin VM List type and false if it is