Add 'dart:debugger' library

sdk/lib/debugger/debugger.dart

Index: sdk/lib/debugger/debugger.dart
diff --git a/sdk/lib/debugger/debugger.dart b/sdk/lib/debugger/debugger.dart
new file mode 100644
index 0000000000000000000000000000000000000000..a18e3b84acf8e7e49452ea24b0906f1598a22a3d
--- /dev/null
+++ b/sdk/lib/debugger/debugger.dart
@@ -0,0 +1,23 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file

[hausner, 2015/05/05 00:16:27]

2015

[Cutch, 2015/05/05 02:38:53]

Done.

+// 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.
+
+/// Programmatically trigger breakpoints.
+library dart.debugger;
+
+/// Programmatically trigger breakpoints.
+class Debugger {
+  /// Trigger a breakpoint. In other words, when invoked, the isolate will
+  /// not return until a debugger continues execution. The behaviour is the same
+  /// regardless of whether or not a debugger is connected.
+  static void breakpoint() {
+    print('Debugger.breakpoint not supported by your embedder.');

[hausner, 2015/05/05 00:16:27]

... by this embedder ... ?

or: on this platform

[Cutch, 2015/05/05 02:38:53]

Done.

+  }
+
+  /// Call [breakpoint] if [expr] is true.
+  static void breakpointIf(bool expr) {
+    if (expr) {
+      breakpoint();
+    }
+  }
+}