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

tests/try/poi/forget_element_test.dart

 // Copyright (c) 2014, 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 of Compiler.forgetElement.
 library trydart.forget_element_test;
 
-import 'package:compiler/src/elements/elements.dart' show
+import 'package:compiler/implementation/elements/elements.dart' show
     AstElement,
     ClassElement,
     Element,
     FunctionElement,
     LocalFunctionElement,
     MetadataAnnotation,
     ScopeContainerElement,
     VariableElement;
 
-import 'package:compiler/src/js_backend/js_backend.dart' show
+import 'package:compiler/implementation/js_backend/js_backend.dart' show
     JavaScriptBackend;
 
-import 'package:compiler/src/tree/tree.dart' as tree;
+import 'package:compiler/implementation/tree/tree.dart' as tree;
 
-import 'package:compiler/src/scanner/scannerlib.dart' show
+import 'package:compiler/implementation/scanner/scannerlib.dart' show
     PartialMetadataAnnotation;
 
-import 'package:compiler/src/elements/visitor.dart' show
+import 'package:compiler/implementation/elements/visitor.dart' show
     ElementVisitor;
 
-import 'package:compiler/src/dart2jslib.dart' show
+import 'package:compiler/implementation/dart2jslib.dart' show
     DartConstantCompiler;
 
-import 'package:compiler/src/universe/universe.dart' show
+import 'package:compiler/implementation/universe/universe.dart' show
     Universe;
 
-import 'package:compiler/src/dart_types.dart' show
+import 'package:compiler/implementation/dart_types.dart' show
     DartType;
 
 import 'compiler_test_case.dart';
 
 import 'forget_element_assertion.dart' show
     assertUnimplementedLocalMetadata;
 
 class ForgetElementTestCase extends CompilerTestCase {
   final int expectedClosureCount;
 
@@ skipping 348 matching lines @@
     // Test that a constant in a parameter initializer is discarded
     // correctly (deeply nested function).
     new ForgetElementTestCase(
         'main() => (() => (([x = const Constant()]) => x)())();'
         ' $CONSTANT_CLASS',
         closureCount: 2,
         constantCount: 1,
         initialValueCount: 1),
 
 ]..addAll(assertUnimplementedLocalMetadata());