Remove support for the DeferredLibrary annotation and remove tests of it

tests/compiler/dart2js_extra/deferred/deferred_class_test.dart

Index: tests/compiler/dart2js_extra/deferred/deferred_class_test.dart
diff --git a/tests/compiler/dart2js_extra/deferred/deferred_class_test.dart b/tests/compiler/dart2js_extra/deferred/deferred_class_test.dart
index ff7e328e82486257caca7a635dae71c19581a47a..3d43f5d0b39ec67e51270fd3174f20d288a54eb1 100644
--- a/tests/compiler/dart2js_extra/deferred/deferred_class_test.dart
+++ b/tests/compiler/dart2js_extra/deferred/deferred_class_test.dart
@@ -7,9 +7,7 @@ import 'package:expect/expect.dart';
 
 import 'dart:async';
 
-@lazy import 'deferred_class_library.dart' as lib;
-
-const lazy = const DeferredLibrary('deferred_class_library');
+import 'deferred_class_library.dart' deferred as lib;
 
 isError(e) => e is Error;
 
@@ -19,7 +17,7 @@ main() {
   Expect.isNull(x);
   int counter = 0;
   asyncStart();
-  lazy.load().then((_) {
+  lib.loadLibrary().then((_) {
     Expect.equals(1, ++counter);
     print('deferred_class_library was loaded');
     x = new lib.MyClass();
@@ -29,7 +27,7 @@ main() {
   Expect.equals(0, counter);
   Expect.isNull(x);
   asyncStart();
-  lazy.load().then((_) {
+  lib.loadLibrary().then((_) {
     Expect.equals(2, ++counter);
     print('deferred_class_library was loaded');
     x = new lib.MyClass();