Make ClosureMirror handle instances of user-defined classes that implement call.

runtime/lib/mirrors_impl.dart

Index: runtime/lib/mirrors_impl.dart
diff --git a/runtime/lib/mirrors_impl.dart b/runtime/lib/mirrors_impl.dart
index 9f48dfd9cba42478e6d0e350d6e70d42b15b8546..7c7331fb53ae502ca2d509235e690ff16e25ca0f 100644
--- a/runtime/lib/mirrors_impl.dart
+++ b/runtime/lib/mirrors_impl.dart
@@ -632,6 +632,14 @@ class _LocalFunctionTypeMirrorImpl extends _LocalClassMirrorImpl
     return _simpleName;
   }
 
+  MethodMirror _callMethod;
+  MethodMirror get callMethod {
+    if (_callMethod == null) {
+      _callMethod = this._FunctionTypeMirror_call_method(_reflectee);
+    }
+    return _callMethod;
+  }
+
   TypeMirror _returnType = null;
   TypeMirror get returnType {
     if (_returnType == null) {
@@ -655,6 +663,9 @@ class _LocalFunctionTypeMirrorImpl extends _LocalClassMirrorImpl
 
   String toString() => "FunctionTypeMirror on '${_n(simpleName)}'";
 
+  MethodMirror _FunctionTypeMirror_call_method(reflectee)
+      native "FunctionTypeMirror_call_method";
+
   static Type _FunctionTypeMirror_return_type(reflectee)
       native "FunctionTypeMirror_return_type";