Be smarter about when disabling tree-shaking.

dart/tests/compiler/dart2js/mirror_tree_shaking_test.dart

Index: dart/tests/compiler/dart2js/mirror_tree_shaking_test.dart
diff --git a/dart/tests/compiler/dart2js/unneeded_part_js_test.dart b/dart/tests/compiler/dart2js/mirror_tree_shaking_test.dart
similarity index 75%
copy from dart/tests/compiler/dart2js/unneeded_part_js_test.dart
copy to dart/tests/compiler/dart2js/mirror_tree_shaking_test.dart
index aa1e641dbdbeb9dc454641db8bc933bd41a9086a..7025c417240f72f8ad3c868ac98e1e13e7ce4a9c 100644
--- a/dart/tests/compiler/dart2js/unneeded_part_js_test.dart
+++ b/dart/tests/compiler/dart2js/mirror_tree_shaking_test.dart
@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// Test that no parts are emitted when deferred loading isn't used.
+// Test that tree-shaking hasn't been turned off.
 
 import 'package:expect/expect.dart';
 import 'memory_source_file_helper.dart';
@@ -24,14 +24,13 @@ main() {
   var provider = new MemorySourceFileProvider();
   void diagnosticHandler(Uri uri, int begin, int end,
                          String message, Diagnostic kind) {
-    if (kind == Diagnostic.VERBOSE_INFO) {
+    if (kind == Diagnostic.VERBOSE_INFO || kind == Diagnostic.WARNING) {
       return;
     }
     throw '$uri:$begin:$end:$message:$kind';
   }
 
   EventSink<String> outputProvider(String name, String extension) {
-    if (name != '') throw 'Attempt to output file "$name.$extension"';
     return new NullSink('$name.$extension');
   }
 
@@ -43,23 +42,23 @@ main() {
                                    []);
   compiler.run(Uri.parse('memory:main.dart'));
   Expect.isFalse(compiler.compilationFailed);
+  Expect.isFalse(compiler.enqueuer.resolution.hasEnqueuedEverything);
+  Expect.isFalse(compiler.enqueuer.codegen.hasEnqueuedEverything);
 }
 
 const Map MEMORY_SOURCE_FILES = const {
-  'main.dart': """
-class Greeting {
-  final message;
-  const Greeting(this.message);
-}
-
-const fisk = const Greeting('Hello, World!');
+  'main.dart': r"""
+import 'dart:mirrors';
 
-main() {
-  var x = fisk;
-  if (new DateTime.now().millisecondsSinceEpoch == 42) {
-    x = new Greeting(\"I\'m confused\");
+class Foo {
+  noSuchMethod(invocation) {
+    print('Invoked ${MirrorSystem.getName(invocation.memberName)}');
+    return reflect('foobar').delegate(invocation);
   }
-  print(x.message);
+}
+
+void main() {
+  print(new Foo().substring(3));
 }
 """,
 };