Add echo and line modes to Stdin.

sdk/lib/io/stdio.dart

Index: sdk/lib/io/stdio.dart
diff --git a/sdk/lib/io/stdio.dart b/sdk/lib/io/stdio.dart
index 31a5c003bb9e82d88ac9cc19585583c35e1d7196..737b8f12f107b97718f7c94fa97186741bc92e90 100644
--- a/sdk/lib/io/stdio.dart
+++ b/sdk/lib/io/stdio.dart
@@ -42,7 +42,7 @@ class _StdinEventSink {
  *
  * Mixing synchronous and asynchronous reads is undefined.
  */
-class Stdin extends _StdStream {
+class Stdin extends _StdStream implements Stream<List<int>> {
   Stdin._(Stream<List<int>> stream) : super(stream);
 
   /**
@@ -98,6 +98,25 @@ class Stdin extends _StdStream {
   }
 
   /**
+   * Enable or disable echo mode on the [Stdin].
+   *
+   * If disabled, input from to console will not be echoed.
+   *
+   * Default depends on the parent process, but usually enabled.
+   */
+  external void set echoMode(bool enabled);
+
+  /**
+   * Enable or disable line mode on the [Stdin].
+   *
+   * If enabled, characters are delayed until a new-line character is entered.
+   * If disabled, characters will be available as typed.
+   *
+   * Default depends on the parent process, but usually enabled.
+   */
+  external void set lineMOde(bool enabled);
+
+  /**
    * Synchronously read a byte from stdin. This call will block until a byte is
    * available.
    *