Fix issue with async callbacks that get called synchronously while running test case function causi…

pkg/unittest/lib/src/test_case.dart

Index: pkg/unittest/lib/src/test_case.dart
===================================================================
--- pkg/unittest/lib/src/test_case.dart	(revision 19336)
+++ pkg/unittest/lib/src/test_case.dart	(working copy)
@@ -78,7 +78,12 @@
 
   Future _runTest() {
     _prepTest();
+    // Increment/decrement callbackFunctionsOutstanding to prevent
+    // synchronous 'async' callbacks from causing the  test to be
+    // marked as complete before the body is completely executed.
+    ++callbackFunctionsOutstanding;
     var f = test();
+    --callbackFunctionsOutstanding;
     if (f is Future) {
       f.then((_) => _finishTest())
        .catchError((e) => fail("${e.error}"));
@@ -204,4 +209,10 @@
   void error(String messageText, [String stack = '']) {
     _complete(ERROR, messageText, stack);
   }
+
+  void markCallbackComplete() {
+    if (--callbackFunctionsOutstanding == 0 && !isComplete) {
+      pass();
+    }
+  }
 }