Remove unused support for disabling error messages

pkg/analyzer/lib/src/generated/error.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 engine.error;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/ast.dart' show AstNode;
 import 'package:analyzer/src/generated/element.dart';
@@ skipping 2458 matching lines @@
       : super(name, message, correction);
 
   @override
   ErrorSeverity get errorSeverity => ErrorType.COMPILE_TIME_ERROR.severity;
 
   @override
   ErrorType get type => ErrorType.COMPILE_TIME_ERROR;
 }
 
 /**
- * An error listener that can be enabled or disabled while executing a function.
- */
-class DisablableErrorListener implements AnalysisErrorListener {
-  /**
-   * The listener to which errors will be reported if this listener is enabled.
-   */
-  final AnalysisErrorListener baseListener;
-
-  /**
-   * A flag indicating whether this listener is currently enabled.
-   */
-  bool enabled = true;
-
-  /**
-   * Initialize a newly created listener to report errors to the given
-   * [baseListener].
-   */
-  DisablableErrorListener(this.baseListener);
-
-  /**
-   * Disable the processing of errors while evaluating the given [function].
-   * Return the value returned by the function.
-   */
-  dynamic disableWhile(dynamic function()) {
-    bool wasEnabled = enabled;
-    try {
-      enabled = false;
-      return function();
-    } finally {
-      enabled = wasEnabled;
-    }
-  }
-
-  /**
-   * Disable the processing of errors while evaluating the given [function].
-   * Return the value returned by the function.
-   */
-  dynamic enableWhile(dynamic function()) {
-    bool wasEnabled = enabled;
-    try {
-      enabled = true;
-      return function();
-    } finally {
-      enabled = wasEnabled;
-    }
-  }
-
-  @override
-  void onError(AnalysisError error) {
-    if (enabled) {
-      baseListener.onError(error);
-    }
-  }
-}
-
-/**
  * An error code associated with an [AnalysisError].
  *
  * Generally, we want to provide messages that consist of three sentences. From
  * the user's perspective these sentences should explain:
  * 1. what is wrong,
  * 2. why is it wrong, and
  * 3. how do I fix it.
  * However, we combine the first two in the [message] and the last in the
  * [correction].
  */
@@ skipping 3128 matching lines @@
    * Initialize a newly created error code to have the given [name].
    */
   const TodoCode(String name) : super(name, "{0}");
 
   @override
   ErrorSeverity get errorSeverity => ErrorSeverity.INFO;
 
   @override
   ErrorType get type => ErrorType.TODO;
 }