Move dart2js from sdk/lib/_internal/compiler to pkg/compiler

pkg/compiler/lib/src/apiimpl.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.
 
 library leg_apiimpl;
 
 import 'dart:async';
 
 import '../compiler.dart' as api;
 import 'dart2jslib.dart' as leg;
 import 'tree/tree.dart' as tree;
 import 'elements/elements.dart' as elements;
-import '../../libraries.dart';
+import 'package:_internal/libraries.dart';
 import 'source_file.dart';
 
 const bool forceIncrementalSupport =
     const bool.fromEnvironment('DART2JS_EXPERIMENTAL_INCREMENTAL_SUPPORT');
 
 class Compiler extends leg.Compiler {
   api.CompilerInputProvider provider;
   api.DiagnosticHandler handler;
   final Uri libraryRoot;
   final Uri packageRoot;
@@ skipping 330 matching lines @@
   }
 
   void diagnoseCrashInUserCode(String message, exception, stackTrace) {
     hasCrashed = true;
     print('$message: ${tryToString(exception)}');
     print(tryToString(stackTrace));
   }
 
   fromEnvironment(String name) => environment[name];
 }