Improve type information and minor clean up

pkg/analyzer/lib/src/context/context.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.context.context;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 998 matching lines @@
         !AnalysisEngine.isDartFileName(librarySource.shortName)) {
       return null;
     }
     return getResult(
         new LibrarySpecificUnit(librarySource, unitSource), RESOLVED_UNIT);
   }
 
   @override
   Object/*=V*/ getResult/*<V>*/(
       AnalysisTarget target, ResultDescriptor/*<V>*/ result) {
-    return _cache.getValue(target, result) as Object/*=V*/;
+    return _cache.getValue(target, result);
   }
 
   @override
   List<Source> getSourcesWithFullName(String path) {
     return analysisCache.getSourcesWithFullName(path);
   }
 
   @override
   bool handleContentsChanged(
       Source source, String originalContents, String newContents, bool notify) {
@@ skipping 1168 matching lines @@
     }
     DartSdk sdk = factory.dartSdk;
     if (sdk == null) {
       throw new IllegalArgumentException(
           "The source factory for an SDK analysis context must have a DartUriResolver");
     }
     return new AnalysisCache(
         <CachePartition>[AnalysisEngine.instance.partitionManager.forSdk(sdk)]);
   }
 }