Don't create part.js when there is no deferred loading.

dart/tests/compiler/dart2js/unneeded_part_js_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // 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.
+
 import 'package:expect/expect.dart';
 import 'memory_source_file_helper.dart';
 
+import '../../../sdk/lib/_internal/compiler/implementation/dart2jslib.dart'
+       show NullSink;
+
 import '../../../sdk/lib/_internal/compiler/compiler.dart'
        show Diagnostic;
 
+import 'dart:async';
+
 main() {
   Uri script = currentDirectory.resolve(nativeToUriPath(new Options().script));
   Uri libraryRoot = script.resolve('../../../sdk/');
   Uri packageRoot = script.resolve('./packages/');
 
   MemorySourceFileProvider.MEMORY_SOURCE_FILES = MEMORY_SOURCE_FILES;
   var provider = new MemorySourceFileProvider();
-  int warningCount = 0;
-  int errorCount = 0;
   void diagnosticHandler(Uri uri, int begin, int end,
                          String message, Diagnostic kind) {
     if (kind == Diagnostic.VERBOSE_INFO) {
       return;
     }
-    if (kind == Diagnostic.ERROR) {
-      errorCount++;
-    } else if (kind == Diagnostic.WARNING) {
-      warningCount++;
-    } else {
-      throw 'unexpected diagnostic $kind: $message';
-    }
+    throw '$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');
   }
 
   Compiler compiler = new Compiler(provider.readStringFromUri,
-                                   (name, extension) => null,
+                                   outputProvider,
                                    diagnosticHandler,
                                    libraryRoot,
                                    packageRoot,
-                                   ['--analyze-only']);
+                                   []);
   compiler.run(Uri.parse('memory:main.dart'));
-  Expect.isTrue(compiler.compilationFailed);
-  Expect.equals(5, errorCount);
-  Expect.equals(1, warningCount);
+  Expect.isFalse(compiler.compilationFailed);
 }
 
 const Map MEMORY_SOURCE_FILES = const {
   'main.dart': """
+class Greeting {
+  final message;
+  const Greeting(this.message);
+}
+
+const fisk = const Greeting('Hello, World!');
+
 main() {
-  for (var x, y in []) {
+  var x = fisk;
+  if (new DateTime.now().millisecondsSinceEpoch == 42) {
+    x = new Greeting(\"I\'m confused\");
   }
-
-  for (var x = 10 in []) {
-  }
-
-  for (x.y in []) { // Also causes a warning "x unresolved".
-  }
-
-  for ((){}() in []) {
-  }
-
-  for (1 in []) {
-  }
+  print(x.message);
 }
-"""
+""",
 };