Fix for an analysis driver test misprint.

pkg/analyzer/test/src/dart/analysis/driver_test.dart

 // Copyright (c) 2016, 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.test.driver;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 365 matching lines @@
     // Remove a file.
     // The cache is flushed.
     driver.removeFile(b);
     expect(driver.test.priorityResults, isEmpty);
   }
 
   test_cachedPriorityResults_flush_onPrioritySetChange() async {
     var a = _p('/test/bin/a.dart');
     var b = _p('/test/bin/b.dart');
     provider.newFile(a, 'var a = 1;');
-    provider.newFile(a, 'var b = 2;');
+    provider.newFile(b, 'var b = 2;');
 
     driver.priorityFiles = [a];
 
     AnalysisResult result1 = await driver.getResult(a);
     expect(driver.test.priorityResults, hasLength(1));
     expect(driver.test.priorityResults, containsPair(a, result1));
 
     // Make "a" and "b" priority.
     // We still have the result for "a" cached.
     driver.priorityFiles = [a, b];
@@ skipping 1668 matching lines @@
    * Return the [provider] specific path for the given Posix [path].
    */
   String _p(String path) => provider.convertPath(path);
 
   static String _md5(String content) {
     return hex.encode(md5.convert(UTF8.encode(content)).bytes);
   }
 }
 
 class _SourceMock extends TypedMock implements Source {}