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

pkg/compiler/samples/compile_loop/compile_loop.dart

 // Copyright (c) 2013, 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.
 
 // This sample demonstrates how to run the compiler in a loop reading
 // all sources from memory, instead of using dart:io.
 library sample.compile_loop;
 
 import 'dart:async';
 
@@ skipping 13 matching lines @@
       return new Future.value(value);
     } else if ('$uri' == 'memory:/main.dart') {
       return new Future.value(source);
     }
     // TODO(ahe): Use new Future.error.
     throw new Exception('Error: Cannot read: $uri');
   }
   void handler(Uri uri, int begin, int end,
                String message, compiler.Diagnostic kind) {
     // TODO(ahe): Remove dart:io import from
-    // ../../implementation/source_file_provider.dart and use
+    // ../../lib/src/source_file_provider.dart and use
     // FormattingDiagnosticHandler instead.
     print({ 'uri': '$uri',
             'begin': begin,
             'end': end,
             'message': message,
             'kind': kind.name });
     if (kind == compiler.Diagnostic.ERROR) {
       throw new Exception('Unexpected error occurred.');
     }
   }
@@ skipping 22 matching lines @@
 
 var greeting = "Hello, World!";
 
 // Displays a greeting.
 void main() {
   // This example uses HTML to display the greeting and it will appear
   // in a nested HTML frame (an iframe).
   document.body.append(new HeadingElement.h1()..appendText(greeting));
 }
 ''';