Fix SDK partitions leak in tests.

pkg/analysis_server/test/abstract_context.dart

 // Copyright (c) 2014, 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 testing.abstract_context;
 
 import 'dart:async';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 150 matching lines @@
     AnalysisEngine.instance.logger = PrintLogger.instance;
   }
 
   void setupResourceProvider() {
     provider = new MemoryResourceProvider();
   }
 
   void tearDown() {
     _context = null;
     provider = null;
+    AnalysisEngine.instance.clearCaches();
     AnalysisEngine.instance.logger = null;
   }
 }
 
 /**
  * Instances of the class [PrintLogger] print all of the errors.
  */
 class PrintLogger implements Logger {
   static final Logger instance = new PrintLogger();
 
@@ skipping 19 matching lines @@
  * [engine.GeneralizingElementVisitor].
  */
 class _ElementVisitorFunctionWrapper extends GeneralizingElementVisitor {
   final _ElementVisitorFunction function;
   _ElementVisitorFunctionWrapper(this.function);
   visitElement(Element element) {
     function(element);
     super.visitElement(element);
   }
 }