Fix error plumbing in WorkItem

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

 // Copyright (c) 2015, 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.src.task.driver;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/context/cache.dart';
@@ skipping 704 matching lines @@
             if (descriptor == null) {
               throw new AnalysisException(
                   'Cannot find task to build $inputResult for $inputTarget');
             }
             return new WorkItem(context, inputTarget, descriptor, inputResult,
                 level + 1, workOrder);
           } on AnalysisException catch (exception, stackTrace) {
             this.exception = new CaughtException(exception, stackTrace);
             return null;
           } catch (exception, stackTrace) {
-            this.exception = new CaughtException(
-                throw new AnalysisException(
-                    'Cannot create work order to build $inputResult for $inputTarget',
-                    exception),
-                stackTrace);
+            this.exception = new CaughtException(exception, stackTrace);
+            throw new AnalysisException(
+                'Cannot create work order to build $inputResult for $inputTarget',
+                this.exception);
             return null;
           }
         }
       } else {
         builder.currentValue = inputEntry.getValue(inputResult);
         if (builder.flushOnAccess) {
           inputEntry.setState(inputResult, CacheState.FLUSHED);
         }
       }
       if (!builder.moveNext()) {
@@ skipping 88 matching lines @@
   final TaskManager taskManager;
 
   _WorkOrderDependencyWalker(this.taskManager, WorkItem startingNode)
       : super(startingNode);
 
   @override
   WorkItem getNextInput(WorkItem node, List<WorkItem> skipInputs) {
     return node.gatherInputs(taskManager, skipInputs);
   }
 }