Move common identifiers, names and selectors to a separate library.

tests/compiler/dart2js/backend_dart/dart_backend_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 "package:expect/expect.dart";
 import 'dart:async';
 import "package:async_helper/async_helper.dart";
 import '../mock_compiler.dart';
 import '../mock_libraries.dart';
 import '../output_collector.dart';
 import 'package:compiler/compiler.dart';
-import 'package:compiler/src/compiler.dart' as leg;
+import 'package:compiler/src/common/names.dart' show Identifiers;
 import 'package:compiler/src/dart_backend/dart_backend.dart';
 import 'package:compiler/src/elements/elements.dart';
 import 'package:compiler/src/tree/tree.dart';
 
 const ioLib = r'''
 library io;
 class Platform {
   static int operatingSystem;
 }
 ''';
@@ skipping 603 matching lines @@
   var src = '''
 main() {
   function localfoo() {}
   localfoo();
 }
 ''';
   MockCompiler compiler = new MockCompiler.internal(emitJavaScript: false);
   asyncTest(() => compiler.init().then((_) {
     assert(compiler.backend is DartBackend);
     compiler.parseScript(src);
-    FunctionElement mainElement = compiler.mainApp.find(leg.Compiler.MAIN);
+    FunctionElement mainElement = compiler.mainApp.find(Identifiers.main);
     compiler.processQueue(compiler.enqueuer.resolution, mainElement);
     PlaceholderCollector collector = collectPlaceholders(compiler, mainElement);
     FunctionExpression mainNode = mainElement.node;
     Block body = mainNode.body;
     FunctionDeclaration functionDeclaration = body.statements.nodes.head;
     FunctionExpression fooNode = functionDeclaration.function;
     LocalPlaceholder fooPlaceholder =
         collector.functionScopes[mainElement].localPlaceholders.first;
     Expect.isTrue(fooPlaceholder.nodes.contains(fooNode.name));
   }));
@@ skipping 460 matching lines @@
   testParametersMinified();
   testDeclarationTypePlaceholders();
   testPlatformLibraryMemberNamesAreFixed();
   testConflictsWithCoreLib();
   testUnresolvedNamedConstructor1();
   testUnresolvedNamedConstructor2();
   testUnresolvedNamedConstructor3();
   testClassAndNamedMixinDeclarations();
 }