Handle stdio redirection in standalone VM

runtime/bin/file_impl.dart

Index: runtime/bin/file_impl.dart
diff --git a/runtime/bin/file_impl.dart b/runtime/bin/file_impl.dart
index d847acb9b8df72debe6f7411b6add5c47c368de4..771a9b9e85692284c7a93a1b9e853fd2115f5e79 100644
--- a/runtime/bin/file_impl.dart
+++ b/runtime/bin/file_impl.dart
@@ -10,6 +10,14 @@ class _FileInputStream extends _BaseDataInputStream implements InputStream {
     _checkScheduleCallbacks();
   }
 
+  _FileInputStream.fromStdio(int fd) {
+    assert(fd == 0);
+    _file = _File._openStdioSync(fd);
+    _length = _file.lengthSync();
+    _streamMarkedClosed = true;
+    _checkScheduleCallbacks();
+  }
+
   int available() {
     return _closed ? 0 : _length - _file.positionSync();
   }
@@ -53,6 +61,11 @@ class _FileOutputStream implements OutputStream {
     _file = file.openSync(mode);
   }
 
+  _FileOutputStream.fromStdio(int fd) {
+    assert(1 <= fd && fd <= 2);
+    _file = _File._openStdioSync(fd);
+  }
+
   bool write(List<int> buffer, [bool copyBuffer = false]) {
     return _write(buffer, 0, buffer.length);
   }
@@ -452,6 +465,7 @@ class _FileUtils {
   static bool truncate(int id, int length) native "File_Truncate";
   static int length(int id) native "File_Length";
   static int flush(int id) native "File_Flush";
+  static int openStdio(int fd) native "File_OpenStdio";
 
   static int checkedOpen(String name, int mode) {
     if (name is !String || mode is !int) return 0;
@@ -618,6 +632,14 @@ class _File implements File {
     return new _RandomAccessFile(id, _name);
   }
 
+  static RandomAccessFile _openStdioSync(int fd) {
+    var id = _FileUtils.openStdio(fd);
+    if (id == 0) {
+      throw new FileIOException("Cannot open stdio file for: $fd");
+    }
+    return new _RandomAccessFile(id, "");
+  }
+
   void fullPath() {
     _asyncUsed = true;
     var handleFullPathResult = (result, ignored) {