Fix dart2js io patch.

sdk/lib/_internal/compiler/implementation/lib/io_patch.dart

Index: sdk/lib/_internal/compiler/implementation/lib/io_patch.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/io_patch.dart b/sdk/lib/_internal/compiler/implementation/lib/io_patch.dart
index a253935b996c1629b7ff9ce0f51941da7b85d951..796bd98887930a893f21af09edd3584c362d547e 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/io_patch.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/io_patch.dart
@@ -87,6 +87,9 @@ patch class _RandomAccessFile {
   patch static _readByte(int id) {
     throw new UnsupportedError("RandomAccessFile._readByte");
   }
+  patch static _read(int id, int bytes) {
+    throw new UnsupportedError("RandomAccessFile._read");
+  }
   patch static _readList(int id, List<int> buffer, int offset, int bytes) {
     throw new UnsupportedError("RandomAccessFile._readList");
   }