Properly rename main methods declared in imported libs.

tests/compiler/dart2js/unparser_test.dart

 // Copyright (c) 2012, 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.
 
 #import('dart:uri');
 #import('parser_helper.dart');
 #import('mock_compiler.dart');
 #import("../../../lib/compiler/compiler.dart");
 #import("../../../lib/compiler/implementation/dart_backend/dart_backend.dart");
 #import("../../../lib/compiler/implementation/elements/elements.dart");
@@ skipping 557 matching lines @@
   var expectedResult =
     'interface I{}'
     'class A<T extends I>{}'
     'interface p_I{}'
     'class p_A<p_T extends p_I>{}'
     'main(){new p_A(); new A();}';
   testDart2DartWithLibrary(mainSrc, librarySrc,
       (String result) { Expect.equals(expectedResult, result); });
 }
 
+testDoubleMains() {
+  var librarySrc = '''
+#library('mylib');
+main() {}
+''';
+  var mainSrc = '''
+#import('mylib.dart', prefix: 'mylib');
+main() {
+  mylib.main();
+}
+''';
+  var expectedResult =
+    'p_main(){}'
+    'main(){p_main();}';
+  testDart2DartWithLibrary(mainSrc, librarySrc,
+      (String result) { Expect.equals(expectedResult, result); });
+}
+
 main() {
   testSignedConstants();
   testGenericTypes();
   testForLoop();
   testEmptyList();
   testClosure();
   testIndexedOperatorDecl();
   testNativeMethods();
   testPrefixIncrements();
   testConstModifier();
@@ skipping 13 matching lines @@
   testConflictLibraryClassRename();
   testDefaultClassWithArgs();
   testClassExtendsWithArgs();
   testStaticInvocation();
   testLibraryGetSet();
   testFieldTypeOutput();
   testDefaultClassNamePlaceholder();
   testFactoryRename();
   testTypeVariablesAreRenamed();
   testClassTypeArgumentBound();
+  testDoubleMains();
 }