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

pkg/analyzer/lib/file_system/file_system.dart

Index: pkg/analyzer/lib/file_system/file_system.dart
diff --git a/pkg/analyzer/lib/file_system/file_system.dart b/pkg/analyzer/lib/file_system/file_system.dart
index 899d6c5bf6227ad7b2ff4b2e8f349f96e0913e88..62c158b12447cd8021f4da0ea0ec1547e2c7b473 100644
--- a/pkg/analyzer/lib/file_system/file_system.dart
+++ b/pkg/analyzer/lib/file_system/file_system.dart
@@ -139,20 +139,6 @@ abstract class ResourceProvider {
   Context get pathContext;
 
   /**
-   * Return a [File] that corresponds to the given [path].
-   * 
-   * A file may or may not exist at this location.
-   */
-  File getFile(String path);
-
-  /**
-   * Return a [Folder] that corresponds to the given [path].
-   * 
-   * A folder may or may not exist at this location.
-   */
-  Folder getFolder(String path);
-
-  /**
    * Return the [Resource] that corresponds to the given [path].
    */
   Resource getResource(String path);