Allow dartk to print out binary Kernel IR results to stdout if requested.

pkg/kernel/lib/kernel.dart

Index: pkg/kernel/lib/kernel.dart
diff --git a/pkg/kernel/lib/kernel.dart b/pkg/kernel/lib/kernel.dart
index 361f59aaa265445c0a472feb4138df8e821c00b3..16eb86adeb78ff1e1eab6c80bf0fdb9f384cde04 100644
--- a/pkg/kernel/lib/kernel.dart
+++ b/pkg/kernel/lib/kernel.dart
@@ -29,13 +29,21 @@ Program loadProgramFromBinary(String path, [Program program]) {
 }
 
 Future writeProgramToBinary(Program program, String path) {
-  var sink = new File(path).openWrite();
+  var sink;
+  if (path == 'null' || path == 'stdout') {
+    sink = new _ByteBuffer();

[asgerf, 2017/03/31 08:40:16]

Is the wrapper necessary?  Could you try this instead?

var sink = stdout.nonBlocking
new BinaryPrinter(sink).writeProgramFile(program)
return sink.flush()

(i.e with stdout.nonBlocking as the sink, but without closing it)

[Emily Fortuna, 2017/03/31 17:46:55]

Ah, that's MUCH better. I didn't know about that. Thanks!

+  } else {
+    sink = new File(path).openWrite();
+  }
+
   var future;
   try {
     new BinaryPrinter(sink).writeProgramFile(program);
   } finally {
     future = sink.close();
   }
+
+  if (sink is _ByteBuffer) print(sink.takeBytes());

[asgerf, 2017/03/31 08:40:16]

Calling toString on a List<int> normally emits something of form [1, 2, 3, ...].
Is this the intention? I think it would make more sense to print the actual byte
stream.

(With the change I suggested above we will not need the print)

[Emily Fortuna, 2017/03/31 17:46:56]

touche. No I hadn't actually tested consuming this input, so I bet I was about
to run into this problem.

   return future;
 }
 
@@ -60,3 +68,25 @@ void writeProgramToText(Program program,
     new File(path).writeAsStringSync('$buffer');
   }
 }
+
+/// Silly wrapper around BytesBuilder that conforms to the Sink interface.

[Johnni Winther, 2017/03/31 06:38:35]

'Silly' -> 'Simple'

[Emily Fortuna, 2017/03/31 17:46:56]

Acknowledged.

+class _ByteBuffer implements Sink<List<int>> {
+  BytesBuilder _builder;
+  bool _open;
+
+  _ByteBuffer()
+      : _open = true,
+        _builder = new BytesBuilder();

[asgerf, 2017/03/31 08:40:16]

You can pass `copy: false` to the BytesBuilder here.

[Emily Fortuna, 2017/03/31 17:46:56]

No longer needed once I took this out.

+
+  void add(List<int> data) {
+    if (_open) {
+      _builder.add(data);
+    }
+  }
+
+  void close() {
+    _open = false;
+  }
+
+  List<int> takeBytes() => _builder.takeBytes();
+}