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

tests/compiler/dart2js/uri_extras_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 'package:compiler/implementation/util/uri_extras.dart';
+import 'package:compiler/src/util/uri_extras.dart';
 
 
 void testRelativize() {
   void c(String expected, String base, String path, bool isWindows) {
     if (isWindows == null) {
       c(expected, base, path, true);
       c(expected, base, path, false);
       return;
     }
 
@@ skipping 69 matching lines @@
     '/Users/other/out.js.map',
     '/Users/person/out.js', true);
 
   c('out.js', '/out.js.map', '/out.js', null);
 
 }
 
 void main() {
   testRelativize();
 }