Add Resource.delete() method.

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 7cc99b74ae2e75e989322ac9c905738477b28661..0acbc142c29af4be068c4d4dca739d9dbf7a7354 100644
--- a/pkg/analyzer/lib/file_system/file_system.dart
+++ b/pkg/analyzer/lib/file_system/file_system.dart
@@ -155,6 +155,13 @@ abstract class Resource {
   String get shortName;
 
   /**
+   * Synchronously deletes this resource and its children.
+   *
+   * Throws an exception if the resource cannot be deleted.
+   */
+  void delete();
+
+  /**
    * Return `true` if absolute [path] references this resource or a resource in
    * this folder.
    */