Tweak reflective_tests _invokeSymbolIfExists to not swallow exceptions

pkg/analyzer/test/reflective_tests.dart

 // Copyright (c) 2014, 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.
 
 library analyzer.test.reflective_tests;
 
 @MirrorsUsed(metaTargets: 'ReflectiveTest')
 import 'dart:mirrors';
 import 'dart:async';
 
@@ skipping 55 matching lines @@
         solo_test(memberName, () {
           return _runFailingTest(classMirror, symbol);
         });
       }
     });
   });
 }
 
 Future _invokeSymbolIfExists(InstanceMirror instanceMirror, Symbol symbol) {
   var invocationResult = null;
+  InstanceMirror closure;
   try {
-    invocationResult = instanceMirror.invoke(symbol, []).reflectee;
+    closure = instanceMirror.getField(symbol);

[Jennifer Messerly, 2016/01/19 23:53:54]

Basically, we get the tearoff:
https://api.dartlang.org/1.13.2/dart-mirrors/ObjectMirror/getField.html

   } on NoSuchMethodError {}
-  if (invocationResult is Future) {
-    return invocationResult;
-  } else {
-    return new Future.value(invocationResult);
+
+  if (closure is ClosureMirror) {
+    invocationResult = closure.apply([]).reflectee;
   }
+  return new Future.value(invocationResult);
 }
 
 /**
  * Run a test that is expected to fail, and confirm that it fails.
  *
  * This properly handles the following cases:
  * - The test fails by throwing an exception
  * - The test returns a future which completes with an error.
  *
  * However, it does not handle the case where the test creates an asynchronous
@@ skipping 18 matching lines @@
  */
 class ReflectiveTest {
   const ReflectiveTest();
 }
 
 /**
  * A marker annotation used to instruct dart2js to keep reflection information
  * for the annotated classes.
  */
 const ReflectiveTest reflectiveTest = const ReflectiveTest();