Make print interceptable.

sdk/lib/_collection_dev/print.dart

Index: sdk/lib/_collection_dev/print.dart
diff --git a/sdk/lib/_collection_dev/print.dart b/sdk/lib/_collection_dev/print.dart
new file mode 100644
index 0000000000000000000000000000000000000000..794b5e9993606a2ad17be36c828c97aa72106695
--- /dev/null
+++ b/sdk/lib/_collection_dev/print.dart
@@ -0,0 +1,18 @@
+// Copyright (c) 2013, 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.
+
+part of dart._collection.dev;
+
+/**

[kasperl, 2013/10/15 13:14:46]

Isn't this a seriously weird place for this functionality to live? What does it
have to do with collections?

[floitsch, 2013/10/15 13:46:49]

_collection_dev is currently our internal library.
We need to rename it to _internal_lib or similar, but since it's not user-facing
it never went high enough on our TODO lists.

+ * This function is set by the first allocation of a Zone.
+ *
+ * Once the function is set the core `print` function calls this closure instead
+ * of [consolePrint].
+ *
+ * This makes it more efficient for dart2js to tree-shake tiny hello-world
+ * programs.
+ */
+Function zonePrint = null;

[kasperl, 2013/10/15 13:14:46]

I'd consider using print as a prefix (so something like printToZone,
printToConsole).

[floitsch, 2013/10/15 13:46:49]

Done.

+
+external void consolePrint(String line);