Enable messages in asserts by default

pkg/analyzer/lib/src/generated/error_verifier.dart

Index: pkg/analyzer/lib/src/generated/error_verifier.dart
diff --git a/pkg/analyzer/lib/src/generated/error_verifier.dart b/pkg/analyzer/lib/src/generated/error_verifier.dart
index 0d6ecf83ff5ee7a4c3b5e83705b724de0a531009..25e35f73925b26ae3f167246f8f6fe281345a14d 100644
--- a/pkg/analyzer/lib/src/generated/error_verifier.dart
+++ b/pkg/analyzer/lib/src/generated/error_verifier.dart
@@ -296,21 +296,10 @@ class ErrorVerifier extends RecursiveAstVisitor<Object> {
   final bool enableSuperMixins;
 
   /**
-   * If `true`, asserts are allowed to take a second argument representing the
-   * assertion failure message (see DEP 37).
-   */
-  final bool enableAssertMessage;
-
-  /**
    * Initialize a newly created error verifier.
    */
-  ErrorVerifier(
-      this._errorReporter,
-      this._currentLibrary,
-      this._typeProvider,
-      this._inheritanceManager,
-      this.enableSuperMixins,
-      this.enableAssertMessage) {
+  ErrorVerifier(this._errorReporter, this._currentLibrary, this._typeProvider,
+      this._inheritanceManager, this.enableSuperMixins) {
     this._isInSystemLibrary = _currentLibrary.source.isInSystemLibrary;
     this._hasExtUri = _currentLibrary.hasExtUri;
     _isEnclosingConstructorConst = false;
@@ -349,14 +338,12 @@ class ErrorVerifier extends RecursiveAstVisitor<Object> {
   @override
   Object visitAssertInitializer(AssertInitializer node) {
     _checkForNonBoolExpression(node);
-    _checkAssertMessage(node);
     return super.visitAssertInitializer(node);
   }
 
   @override
   Object visitAssertStatement(AssertStatement node) {
     _checkForNonBoolExpression(node);
-    _checkAssertMessage(node);
     return super.visitAssertStatement(node);
   }
 
@@ -1302,18 +1289,6 @@ class ErrorVerifier extends RecursiveAstVisitor<Object> {
   }
 
   /**
-   * If the given [assertion] specifies a message, verify that support
-   * for assertions with messages is enabled.
-   */
-  void _checkAssertMessage(Assertion assertion) {
-    Expression expression = assertion.message;
-    if (expression != null && !enableAssertMessage) {
-      _errorReporter.reportErrorForNode(
-          CompileTimeErrorCode.EXTRA_ARGUMENT_TO_ASSERT, expression);
-    }
-  }
-
-  /**
    * Given a list of [directives] that have the same prefix, generate an error
    * if there is more than one import and any of those imports is deferred.
    *