Move parser helper classes to own files and clean them up.

pkg/front_end/lib/src/fasta/parser/member_kind.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.
+
+library fasta.parser.member_kind;
+
+enum MemberKind {
+  /// A catch block, not a real member.
+  Catch,
+
+  /// A factory
+  Factory,
+
+  /// Old-style typedef.
+  FunctionTypeAlias,
+
+  /// Old-style function-typed parameter, not a real member.
+  FunctionTypedParameter,
+
+  /// A generalized function type, not a real member.
+  GeneralizedFunctionType,
+
+  /// A local function.
+  Local,
+
+  /// A non-static method in a class (including constructors).
+  NonStaticMethod,
+
+  /// A static method in a class.
+  StaticMethod,
+
+  /// A top-level method.
+  TopLevelMethod,
+
+  /// An instance field in a class.
+  NonStaticField,
+
+  /// A static field in a class.
+  StaticField,
+
+  /// A top-level field.
+  TopLevelField,
+}