Revert "Package map source factory support" [TBR].

pkg/analyzer/lib/file_system/physical_file_system.dart

Index: pkg/analyzer/lib/file_system/physical_file_system.dart
diff --git a/pkg/analyzer/lib/file_system/physical_file_system.dart b/pkg/analyzer/lib/file_system/physical_file_system.dart
index b8fdcf17199a71049c05b49f9765d16bfa873e2d..d9497df78ae7cdbbc3da69bd8202cdd4ddca8af9 100644
--- a/pkg/analyzer/lib/file_system/physical_file_system.dart
+++ b/pkg/analyzer/lib/file_system/physical_file_system.dart
@@ -41,17 +41,13 @@ class PhysicalResourceProvider implements ResourceProvider {
   Context get pathContext => io.Platform.isWindows ? windows : posix;
 
   @override
-  File getFile(String path) => new _PhysicalFile(new io.File(path));
-
-  @override
-  Folder getFolder(String path) => new _PhysicalFolder(new io.Directory(path));
-
-  @override
   Resource getResource(String path) {
     if (io.FileSystemEntity.isDirectorySync(path)) {
-      return getFolder(path);
+      io.Directory directory = new io.Directory(path);
+      return new _PhysicalFolder(directory);
     } else {
-      return getFile(path);
+      io.File file = new io.File(path);
+      return new _PhysicalFile(file);
     }
   }