Remove the checker and corresponding dead code

lib/strong_mode.dart

-// Copyright (c) 2015, 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.
-
-/// Types needed to implement "strong" checking in the Dart analyzer. This is
-/// intended to be used by `analyzer_cli` and `analysis_server` packages.
-library dev_compiler.strong_mode;
-
-import 'package:analyzer/src/generated/engine.dart'
-    show
-        AnalysisContext,
-        AnalysisContextImpl,
-        AnalysisEngine,
-        AnalysisErrorInfo,
-        AnalysisErrorInfoImpl;
-import 'package:analyzer/src/generated/error.dart'
-    show
-        AnalysisError,
-        AnalysisErrorListener,
-        CompileTimeErrorCode,
-        ErrorCode,
-        ErrorSeverity,
-        HintCode,
-        StaticTypeWarningCode;
-import 'package:analyzer/src/generated/source.dart' show Source;
-import 'package:args/args.dart';
-
-import 'src/analysis_context.dart' show enableDevCompilerInference;
-import 'src/checker/checker.dart' show CodeChecker;
-import 'src/checker/rules.dart' show TypeRules;
-
-/// A type checker for Dart code that operates under stronger rules, and has
-/// the ability to do local type inference in some situations.
-// TODO(jmesserly): remove this class.
-class StrongChecker {
-  final AnalysisContext _context;
-  final CodeChecker _checker;
-  final _ErrorCollector _reporter;
-
-  StrongChecker._(this._context, this._checker, this._reporter);
-
-  factory StrongChecker(AnalysisContext context, StrongModeOptions options) {
-    // TODO(vsm): Remove this once analyzer_cli is completely switched to the
-    // task model.
-    if (!AnalysisEngine.instance.useTaskModel) {
-      enableDevCompilerInference(context, options);
-      var rules = new TypeRules(context.typeProvider);
-      var reporter = new _ErrorCollector(options.hints);
-      var checker = new CodeChecker(rules, reporter);
-      return new StrongChecker._(context, checker, reporter);
-    }
-    return new StrongChecker._(context, null, null);
-  }
-
-  /// Computes and returns DDC errors for the [source].
-  AnalysisErrorInfo computeErrors(Source source) {
-    var errors = new List<AnalysisError>();
-    if (_checker != null) {
-      _reporter.errors = errors;
-
-      for (Source librarySource in _context.getLibrariesContaining(source)) {
-        var resolved = _context.resolveCompilationUnit2(source, librarySource);
-        _checker.visitCompilationUnit(resolved);
-      }
-      _reporter.errors = null;
-    }
-    return new AnalysisErrorInfoImpl(errors, _context.getLineInfo(source));
-  }
-}
-
-class _ErrorCollector implements AnalysisErrorListener {
-  List<AnalysisError> errors;
-  final bool hints;
-  _ErrorCollector(this.hints);
-
-  void onError(AnalysisError error) {
-    // Unless DDC hints are requested, filter them out.
-    var HINT = ErrorSeverity.INFO.ordinal;
-    if (hints || error.errorCode.errorSeverity.ordinal > HINT) {
-      errors.add(error);
-    }
-  }
-}
-
-// TODO(jmesserly): this type is dead now. It's preserved because analyzer_cli
-// passes the `hints` option.
-class StrongModeOptions {
-  /// Whether to include hints about dynamic invokes and runtime checks.
-  // TODO(jmesserly): this option is not used yet by DDC server mode or batch
-  // compile to JS.
-  final bool hints;
-
-  const StrongModeOptions({this.hints: false});
-
-  StrongModeOptions.fromArguments(ArgResults args, {String prefix: ''})
-      : hints = args[prefix + 'hints'];
-
-  static ArgParser addArguments(ArgParser parser,
-      {String prefix: '', bool hide: false}) {
-    return parser
-      ..addFlag(prefix + 'hints',
-          help: 'Display hints about dynamic casts and dispatch operations',
-          defaultsTo: false,
-          hide: hide);
-  }
-
-  bool operator ==(Object other) {
-    if (other is! StrongModeOptions) return false;
-    StrongModeOptions s = other;
-    return hints == s.hints;
-  }
-}