Add prefix to path import to work around breaking change

pkg/analyzer/test/file_system/physical_resource_provider_test.dart

Index: pkg/analyzer/test/file_system/physical_resource_provider_test.dart
diff --git a/pkg/analyzer/test/file_system/physical_resource_provider_test.dart b/pkg/analyzer/test/file_system/physical_resource_provider_test.dart
index 07b62e21622e5961858f702a4d7c44281c64dc43..39ac5dcfa4d41091f729dff256fc42aa28e82ac6 100644
--- a/pkg/analyzer/test/file_system/physical_resource_provider_test.dart
+++ b/pkg/analyzer/test/file_system/physical_resource_provider_test.dart
@@ -11,7 +11,7 @@ import 'dart:io' as io;
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/physical_file_system.dart';
 import 'package:analyzer/src/generated/source_io.dart';
-import 'package:path/path.dart';
+import 'package:path/path.dart' as pathos;
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:watcher/watcher.dart';
@@ -30,6 +30,9 @@ var _isFile = new isInstanceOf<File>();
 var _isFileSystemException = new isInstanceOf<FileSystemException>();
 var _isFolder = new isInstanceOf<Folder>();
 
+String join(String part1, [String part2, String part3]) =>
+    pathos.join(part1, part2, part3);
+
 @reflectiveTest
 class FileTest extends _BaseTest {
   String path;
@@ -180,7 +183,7 @@ class FileTest extends _BaseTest {
   }
 
   void test_resolveSymbolicLinksSync_links() {
-    Context pathContext = PhysicalResourceProvider.INSTANCE.pathContext;
+    pathos.Context pathContext = PhysicalResourceProvider.INSTANCE.pathContext;
     String pathA = pathContext.join(tempPath, 'a');
     String pathB = pathContext.join(pathA, 'b');
     new io.Directory(pathB).createSync(recursive: true);
@@ -440,7 +443,7 @@ class PhysicalResourceProviderTest extends _BaseTest {
   test_getFolder_trailingSeparator() {
     String path = tempPath;
     PhysicalResourceProvider provider = PhysicalResourceProvider.INSTANCE;
-    Folder folder = provider.getFolder('$path$separator');
+    Folder folder = provider.getFolder('$path${pathos.separator}');
     expect(folder.path, path);
   }