Introduce "platform configurations" to replace categories and libraries.dart.

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 'dart:io' as io;
 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/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';
 
@@ skipping 34 matching lines @@
   fileUri(path) => new Uri(scheme: 'file', path: path);
 
   final scriptUri = fileUri('script.dart');
   final libUri = fileUri('mylib.dart');
 
   provider(uri) {
     if (uri == scriptUri) return new Future.value(mainSrc);
     if (uri.toString() == libUri.toString()) {
       return new Future.value(librarySrc);
     }
-    if (uri.path.endsWith('/core.dart')) {
+    if (uri.path.endsWith('/dart2dart.platform')) {
+      return new io.File.fromUri(uri).readAsBytes();
+    } else if (uri.path.endsWith('/core.dart')) {
       return new Future.value(buildLibrarySource(DEFAULT_CORE_LIBRARY));
     } else if (uri.path.endsWith('/core_patch.dart')) {
       return new Future.value(DEFAULT_PATCH_CORE_SOURCE);
     } else if (uri.path.endsWith('/io.dart')) {
       return new Future.value(ioLib);
     } else if (uri.path.endsWith('/js_helper.dart')) {
       return new Future.value(buildLibrarySource(DEFAULT_JS_HELPER_LIBRARY));
     } else if (uri.path.endsWith('/html_dart2js.dart')) {
       // TODO(smok): The file should change to html_dartium at some point.
       return new Future.value(htmlLib);
     } else if (uri.path.endsWith('/foreign_helper.dart')) {
       return new Future.value(
           buildLibrarySource(DEFAULT_FOREIGN_HELPER_LIBRARY));
     } else if (uri.path.endsWith('/isolate_helper.dart')) {
       return new Future.value(
           buildLibrarySource(DEFAULT_ISOLATE_HELPER_LIBRARY));
     }
     return new Future.value('');
   }
 
   handler(uri, begin, end, message, kind) {
     if (identical(kind, Diagnostic.ERROR) || identical(kind, Diagnostic.CRASH)) {
       Expect.fail('$uri: $begin-$end: $message [$kind]');
     }
   }
 
   final options = <String>['--output-type=dart'];
   // Some tests below are using dart:io.
-  options.add('--categories=Client,Server');
   if (minify) options.add('--minify');
   if (stripTypes) options.add('--force-strip=types');
 
   asyncTest(() {
     OutputCollector outputCollector = new OutputCollector();
     return compile(
         scriptUri,
-        fileUri('libraryRoot/'),
+        Uri.base.resolve('sdk/'),
         fileUri('packageRoot/'),
         provider,
         handler,
         options,
         outputCollector).then((_) {
       String code = outputCollector.getOutput('', 'dart');
       Expect.equals(expectedResult, code,
           'expected:\n$expectedResult\nactual:\n$code');
     });
   });
@@ skipping 999 matching lines @@
   testParametersMinified();
   testDeclarationTypePlaceholders();
   testPlatformLibraryMemberNamesAreFixed();
   testConflictsWithCoreLib();
   testUnresolvedNamedConstructor1();
   testUnresolvedNamedConstructor2();
   testUnresolvedNamedConstructor3();
   testClassAndNamedMixinDeclarations();
 }