Move the status file parser into its own package.

tools/testing/dart/environment.dart

 // Copyright (c) 2017, 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:status_file/environment.dart';
+
 import 'configuration.dart';
 
 typedef String _LookUpFunction(Configuration configuration);
 typedef bool _BoolLookUpFunction(Configuration configuration);
 
 // TODO(29756): Instead of synthesized negated variables like "unchecked",
 // consider adding support for "!" to status expressions.
 final _variables = {
   "analyzer": new _Variable.bool((c) => c.compiler == Compiler.dart2analyzer),
   "arch": new _Variable((c) => c.architecture.name, Architecture.names),
@@ skipping 29 matching lines @@
   if (configuration.runtime == Runtime.firefox) return 'ff';
 
   return configuration.runtime.name;
 }
 
 /// Defines the variables that are available for use inside a status file
 /// section header.
 ///
 /// These mostly map to command line arguments with the same name, though this
 /// is only a subset of the full set of command line arguments.
-class Environment {
+class ConfigurationEnvironment implements Environment {
+  /// The configuration where variable data is found.
+  final Configuration _configuration;
+
+  ConfigurationEnvironment(this._configuration);
+
   /// Validates that the variable with [name] exists and can be compared
   /// against [value].
   ///
   /// If any errors are found, adds them to [errors].
-  static void validate(String name, String value, List<String> errors) {
+  void validate(String name, String value, List<String> errors) {
     var variable = _variables[name];
     if (variable == null) {
       errors.add('Unknown variable "$name".');
       return;
     }
 
     // The "builder_tag" variable doesn't have an enumerated set of values.
     if (variable.allowedValues.isEmpty) return;
 
     if (!variable.allowedValues.contains(value)) {
       errors.add(
           'Variable "$name" cannot have value "$value". Allowed values are:\n' +
               variable.allowedValues.join(', ') +
               '.');
     }
   }
 
-  /// The configuration where variable data is found.
-  final Configuration _configuration;
-
-  Environment(this._configuration);
-
   /// Looks up the value of the variable with [name].
   String lookUp(String name) {
     var variable = _variables[name];
     if (variable == null) {
       // This shouldn't happen since we validate variables before evaluating
       // expressions.
       throw new ArgumentError('Unknown variable "$variable".');
     }
 
     return variable.lookUp(_configuration);
@@ skipping 15 matching lines @@
   _Variable(this._lookUp, Iterable<String> allowed)
       : allowedValues = allowed.toList();
 
   /// Creates a Boolean variable with allowed values "true" and "false".
   _Variable.bool(_BoolLookUpFunction lookUp)
       : _lookUp = ((configuration) => lookUp(configuration).toString()),
         allowedValues = const ["true", "false"];
 
   String lookUp(Configuration configuration) => _lookUp(configuration);
 }