Implement messages in assert() in dev_compiler.

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/runtime.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.
 
 library dart._runtime;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'dart:_foreign_helper' show JS, JSExportName, rest, spread;
 import 'dart:_interceptors' show JSArray;
-import 'dart:_js_helper' show SyncIterable, BooleanConversionAssertionError,
-  CastErrorImplementation, TypeErrorImplementation,
-  StrongModeCastError, StrongModeTypeError, StrongModeErrorImplementation,
-  getTraceFromException, Primitives;
+import 'dart:_js_helper'
+    show
+        AssertionErrorWithMessage,
+        BooleanConversionAssertionError,
+        CastErrorImplementation,
+        getTraceFromException,
+        Primitives,
+        TypeErrorImplementation,
+        StrongModeCastError,
+        StrongModeErrorImplementation,
+        StrongModeTypeError,
+        SyncIterable;
 
 part 'classes.dart';
 part 'rtti.dart';
 part 'types.dart';
 part 'errors.dart';
 part 'generators.dart';
 part 'operations.dart';
 part 'utils.dart';
 
 @JSExportName('global')
 final global_ = JS('', 'typeof window == "undefined" ? global : window');
 final JsSymbol = JS('', 'Symbol');