Add 'toString' method to NativeBehavior

pkg/compiler/lib/src/native/behavior.dart

Index: pkg/compiler/lib/src/native/behavior.dart
diff --git a/pkg/compiler/lib/src/native/behavior.dart b/pkg/compiler/lib/src/native/behavior.dart
index 0d3ca8164ba2a0e96429c85ab980e818184910ac..5b0462dbf86f415565de272557346f46eac25763 100644
--- a/pkg/compiler/lib/src/native/behavior.dart
+++ b/pkg/compiler/lib/src/native/behavior.dart
@@ -6,13 +6,13 @@ part of native;
 
 /// This class is a temporary work-around until we get a more powerful DartType.
 class SpecialType {
-final String name;
-const SpecialType._(this.name);
+  final String name;
+  const SpecialType._(this.name);
 
-/// The type Object, but no subtypes:
-static const JsObject = const SpecialType._('=Object');
+  /// The type Object, but no subtypes:
+  static const JsObject = const SpecialType._('=Object');
 
-int get hashCode => name.hashCode;
+  int get hashCode => name.hashCode;
 }
 
 /**
@@ -59,6 +59,13 @@ class NativeBehavior {
 
   final SideEffects sideEffects = new SideEffects.empty();
 
+  String toString() {
+    return 'NativeBehavior(returns: ${typesReturned}, '
+        'creates: ${typesInstantiated}, '
+        'sideEffects: ${sideEffects})';
+  }
+
+
   /// Processes the type specification string of a call to JS and stores the
   /// result in the [typesReturned] and [typesInstantiated]. It furthermore
   /// computes the side effects, and, if given, invokes [setSideEffects] with