Refactor and clean up the status file parsing code.

tools/testing/dart/runtime_configuration.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.
 
 library runtime_configuration;
 
 import 'dart:io' show Directory, File;
 
 import 'compiler_configuration.dart' show CommandArtifact;
 
 // TODO(ahe): Remove this import, we can precompute all the values required
 // from TestSuite once the refactoring is complete.
 import 'test_suite.dart' show TestSuite, TestUtils;
 
 import 'test_runner.dart' show Command, CommandBuilder;
 
 /// Describes the commands to run a given test case or its compiled output.
 ///
 /// A single runtime configuration object exists per test suite, and is thus
 /// shared between multiple test cases, it should not be mutated after
 /// construction.
 //
 // TODO(ahe): I expect this class will become abstract very soon.
 class RuntimeConfiguration {
   // TODO(ahe): Remove this constructor and move the switch to
   // test_options.dart.  We probably want to store an instance of
   // [RuntimeConfiguration] in [configuration] there.
-  factory RuntimeConfiguration(Map configuration) {
+  factory RuntimeConfiguration(Map<String, dynamic> configuration) {
     String runtime = configuration['runtime'];
     bool useBlobs = configuration['use_blobs'];
 
     switch (runtime) {
       case 'ContentShellOnAndroid':
       case 'DartiumOnAndroid':
       case 'chrome':
       case 'chromeOnAndroid':
       case 'dartium':
       case 'ff':
@@ skipping 318 matching lines @@
 class DummyRuntimeConfiguration extends DartVmRuntimeConfiguration {
   List<Command> computeRuntimeCommands(
       TestSuite suite,
       CommandBuilder commandBuilder,
       CommandArtifact artifact,
       List<String> arguments,
       Map<String, String> environmentOverrides) {
     throw "Unimplemented runtime '$runtimeType'";
   }
 }