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

tests/compiler/dart2js/mock_libraries.dart

Index: tests/compiler/dart2js/mock_libraries.dart
diff --git a/tests/compiler/dart2js/mock_libraries.dart b/tests/compiler/dart2js/mock_libraries.dart
index 37135b2274de5de84fbbecc025b6bc147e4c4251..b31ef33b3cfa32092fe5dfc3f9906fdb5523aba9 100644
--- a/tests/compiler/dart2js/mock_libraries.dart
+++ b/tests/compiler/dart2js/mock_libraries.dart
@@ -6,6 +6,43 @@
 
 library mock_libraries;
 
+const DEFAULT_PLATFORM_CONFIG = """
+[libraries]

[Johnni Winther, 2015/10/30 10:38:39]

Shouldn't this be empty for the MockCompiler?

[sigurdm, 2015/10/30 11:38:27]

No - but most of the lines are not needed.

Done.

+async:async/async.dart
+_chrome:_chrome/dart2js/chrome_dart2js.dart
+collection:collection/collection.dart
+convert:convert/convert.dart
+core:core/core.dart
+developer:developer/developer.dart
+html:html/dart2js/html_dart2js.dart
+html_common:html/html_common/html_common_dart2js.dart
+indexed_db:indexed_db/dart2js/indexed_db_dart2js.dart
+io:unsupported:blah
+isolate:isolate/isolate.dart
+js:js/dart2js/js_dart2js.dart
+math:math/math.dart
+mirrors:mirrors/mirrors.dart
+nativewrappers:html/dart2js/nativewrappers.dart
+typed_data:typed_data/typed_data.dart
+_native_typed_data:_internal/js_runtime/lib/native_typed_data.dart
+svg:svg/dart2js/svg_dart2js.dart
+web_audio:web_audio/dart2js/web_audio_dart2js.dart
+web_gl:web_gl/dart2js/web_gl_dart2js.dart
+web_sql:web_sql/dart2js/web_sql_dart2js.dart
+_internal:internal/internal.dart
+_js_helper:_internal/js_runtime/lib/js_helper.dart
+_interceptors:_internal/js_runtime/lib/interceptors.dart
+_foreign_helper:_internal/js_runtime/lib/foreign_helper.dart
+_isolate_helper:_internal/js_runtime/lib/isolate_helper.dart
+_js_mirrors:_internal/js_runtime/lib/js_mirrors.dart
+_js_names:_internal/js_runtime/lib/js_names.dart
+_js_primitives:_internal/js_runtime/lib/js_primitives.dart
+_mirror_helper:_internal/js_runtime/lib/mirror_helper.dart
+_js_embedded_names:_internal/js_runtime/lib/shared/embedded_names.dart
+_async_await_error_codes:_internal/js_runtime/lib/shared/async_await_error_codes.dart
+_metadata:html/html_common/metadata.dart
+""";
+
 String buildLibrarySource(
     Map<String, String> elementMap,
     [Map<String, String> additionalElementMap = const <String, String>{}]) {