Move delete/deleteSync up to FileSystemEntity, with a shared documentation.

sdk/lib/_internal/lib/io_patch.dart

Index: sdk/lib/_internal/lib/io_patch.dart
diff --git a/sdk/lib/_internal/lib/io_patch.dart b/sdk/lib/_internal/lib/io_patch.dart
index fc29425912966587c177893c4fbfdacfdff59cc8..04ee3a980d28b04e6e863370bce5661944091487 100644
--- a/sdk/lib/_internal/lib/io_patch.dart
+++ b/sdk/lib/_internal/lib/io_patch.dart
@@ -18,8 +18,8 @@ patch class _Directory {
   patch static _create(String path) {
     throw new UnsupportedError("Directory._create");
   }
-  patch static _delete(String path, bool recursive) {
-    throw new UnsupportedError("Directory._delete");
+  patch static _deleteNative(String path, bool recursive) {
+    throw new UnsupportedError("Directory._deleteNative");
   }
   patch static _rename(String path, String newPath) {
     throw new UnsupportedError("Directory._rename");
@@ -74,11 +74,11 @@ patch class _File {
   patch static _linkTarget(String path) {
     throw new UnsupportedError("File._linkTarget");
   }
-  patch static _delete(String path) {
-    throw new UnsupportedError("File._delete");
+  patch static _deleteNative(String path) {
+    throw new UnsupportedError("File._deleteNative");
   }
-  patch static _deleteLink(String path) {
-    throw new UnsupportedError("File._deleteLink");
+  patch static _deleteLinkNative(String path) {
+    throw new UnsupportedError("File._deleteLinkNative");
   }
   patch static _rename(String oldPath, String newPath) {
     throw new UnsupportedError("File._rename");