Fixed the last unit test that was failing with the new task model

pkg/analyzer/lib/src/task/driver.dart

Index: pkg/analyzer/lib/src/task/driver.dart
diff --git a/pkg/analyzer/lib/src/task/driver.dart b/pkg/analyzer/lib/src/task/driver.dart
index e4210d50ec5e88f9c0f2855d6ae038ba5b420627..8daa5cfe08d0e1839aa5be0742a9c48e81ed5f89 100644
--- a/pkg/analyzer/lib/src/task/driver.dart
+++ b/pkg/analyzer/lib/src/task/driver.dart
@@ -102,7 +102,12 @@ class AnalysisDriver {
       WorkOrder workOrder = createWorkOrderForResult(target, result);
       if (workOrder != null) {
         while (workOrder.moveNext()) {
+//          AnalysisTask previousTask = task;
+//          String message = workOrder.current.toString();

[scheglov, 2015/09/10 20:35:38]

Do you still need this?

[Brian Wilkerson, 2015/09/10 21:00:31]

Technically, no, but it was *very* useful for debugging and I expect to use it
again. Basically, this method returns 'null' if a task fails with an exception,
and after this method returns it's very hard to figure out what the exception
was. The commented out code propagates the exception so that tests will include
the stack trace in their output.

           task = performWorkItem(workOrder.current);
+//          if (task == null) {
+//            throw new AnalysisException(message, previousTask.caughtException);
+//          }
         }
       }
       return task;