Fix hints in the analyzer package.

pkg/analyzer/lib/task/model.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.task.model;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/engine.dart' hide AnalysisTask;
 import 'package:analyzer/src/generated/java_engine.dart';
@@ skipping 193 matching lines @@
       }
       stopwatch.start();
       //
       // Actually perform the task.
       //
       try {
         internalPerform();
       } finally {
         stopwatch.stop();
       }
-    } on AnalysisException catch (exception) {
+    } on AnalysisException {
       rethrow;
     } catch (exception, stackTrace) {
       throw new AnalysisException(
           'Unexpected exception while performing $description',
           new CaughtException(exception, stackTrace));
     }
   }
 }
 
 /**
@@ skipping 149 matching lines @@
    * be computed, or `false` if the inputs have been computed.
    *
    * It is safe to invoke [moveNext] after it has returned `false`. In this case
    * [moveNext] has no effect and will again return `false`.
    *
    * Throws a [StateError] if the value of the current result has not been
    * provided using [currentValue].
    */
   bool moveNext();
 }