Add browser-compatible version.

lib/src/browser/html_io.dart

Index: lib/src/browser/html_io.dart
diff --git a/lib/src/browser/html_io.dart b/lib/src/browser/html_io.dart
new file mode 100644
index 0000000000000000000000000000000000000000..2896967db50e2e7e09c555bab0feb7424087c0fc
--- /dev/null
+++ b/lib/src/browser/html_io.dart
@@ -0,0 +1,60 @@
+// Copyright (c) 2016, 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.
+
+import "dart:async" show Future, Stream;
+import "dart:convert" show Encoding, LATIN1, UTF8;
+import "dart:html";
+import "dart:typed_data" show Uint8List, ByteBuffer;
+
+/// Reads the bytes of a URI as a stream of bytes.
+Stream<List<int>> readAsStream(Uri uri) async* {
+  // TODO(lrn): Should file be run through XmlHTTPRequest too?
+  if (uri.scheme == "http" || uri.scheme == "https") {
+    // TODO: Stream in chunks if DOM has a way to do so.
+    List<int> response = await _httpGetBytes(uri);
+    yield response;
+    return;
+  }
+  if (uri.scheme == "data") {
+    yield uri.data.contentAsBytes();
+    return;
+  }
+  throw new UnsupportedError("Unsupported scheme: $uri");
+}
+
+/// Reads the bytes of a URI as a list of bytes.
+Future<List<int>> readAsBytes(Uri uri) async {
+  if (uri.scheme == "http" || uri.scheme == "https") {
+    return _httpGetBytes(uri);
+  }
+  if (uri.scheme == "data") {
+    return uri.data.contentAsBytes();
+  }
+  throw new UnsupportedError("Unsupported scheme: $uri");
+}
+
+/// Reads the bytes of a URI as a string.
+Future<String> readAsString(Uri uri, Encoding encoding) async {
+  if (uri.scheme == "http" || uri.scheme == "https") {
+    // Fetch as string if the encoding is expected to be understood,
+    // otherwise fetch as bytes and do decoding using the encoding.
+    if (encoding != null) {
+      return encoding.decode(await _httpGetBytes(uri));
+    }
+    return HttpRequest.getString(uri.toString());
+  }
+  if (uri.scheme == "data") {
+    return uri.data.contentAsString(encoding: encoding);
+  }
+  throw new UnsupportedError("Unsupported scheme: $uri");
+}
+
+Future<List<int>> _httpGetBytes(Uri uri) {
+  return HttpRequest
+      .request(uri.toString(), responseType: "arraybuffer")
+      .then((request) {
+    ByteBuffer data = request.response;
+    return data.asUint8List();
+  });
+}