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

tests/compiler/dart2js/analyze_only_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.
 
 // Smoke test of the dart2js compiler API.
 library analyze_only;
 
 import "package:expect/expect.dart";
 import 'dart:async';
 import "package:async_helper/async_helper.dart";
@@ skipping 31 matching lines @@
   print('options: $options\n');
   asyncStart();
   OutputCollector outputCollector = new OutputCollector();
   Future<CompilationResult> result =
       compile(new Uri(scheme: 'main'),
               new Uri(scheme: 'lib', path: '/'),
               new Uri(scheme: 'package', path: '/'),
               localProvider, localHandler, options, outputCollector);
   result.then((_) {
     onValue(outputCollector.getOutput('', 'js'), errors, warnings);
-  }, onError: (e) {
-    throw 'Compilation failed: ${Error.safeToString(e)}';
+  }, onError: (e, st) {
+    throw 'Compilation failed: ${e} ${st}';
   }).then(asyncSuccess).catchError((error, stack) {
     print('\n\n-----------------------------------------------');
     print('main source:\n$main');
     print('options: $options\n');
     print('threw:\n $error\n$stack');
     print('-----------------------------------------------\n\n');
     throw error;
   });
 }
 
@@ skipping 113 matching lines @@
   // --analyze-signatures-only implies --analyze-only
   runCompiler(
     "",
     [Flags.analyzeSignaturesOnly, Flags.analyzeAll],
     (String code, List errors, List warnings) {
       Expect.isNull(code);
       Expect.isTrue(errors.isEmpty);
       Expect.isTrue(warnings.isEmpty);
     });
 }