Move tools to tool folder.

pkg/front_end/lib/compiler_options.dart

 // Copyright (c) 2016, 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 front_end.compiler_options;
 
 import 'package:front_end/src/base/performace_logger.dart';
 import 'package:front_end/src/byte_store/byte_store.dart';
 import 'package:kernel/target/targets.dart' show Target;
 
@@ skipping 199 matching lines @@
   ///
   /// The kernel `Program` API includes a `uriToSource` map field that is used
   /// to embed the entire contents of the source files. This part of the kernel
   /// API is in flux and it is not necessary for some tools. Today it is used
   /// for translating error locations and stack traces in the VM.
   // TODO(sigmund): change the default.
   bool embedSourceText = true;
 
   /// Whether the compiler should throw as soon as it encounters a
   /// compilation error.
-  // TODO(sigmund): change the default (issue #30194).
-  bool throwOnErrors = true;
+  ///
+  /// Typically used by developers to debug internals of the compiler.
+  bool throwOnErrorsForDebugging = false;
 
   /// Whether the compiler should throw as soon as it encounters a
   /// compilation warning.
   ///
   /// Typically used by developers to debug internals of the compiler.
-  bool throwOnWarnings = false;
+  bool throwOnWarningsForDebugging = false;
 
   /// Whether the compiler should throw as soon as it encounters a
   /// compilation nit.
   ///
   /// Typically used by developers to debug internals of the compiler.
-  bool throwOnNits = false;
+  bool throwOnNitsForDebugging = false;
 }