Implement messages in assert() in dev_compiler.

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/operations.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.
 
 /// This library defines runtime operations on objects used by the code
 /// generator.
 part of dart._runtime;
 
 class InvocationImpl extends Invocation {
   final Symbol memberName;
@@ skipping 294 matching lines @@
   var f = obj != null ? JS('', '#[#]', obj, symbol) : null;
   var ftype = getMethodType(obj, symbol);
   return _checkAndCall(f, ftype, obj, typeArgs, args, displayName);
 }
 
 dsend(obj, method, @rest args) => _callMethod(obj, method, null, args, method);
 
 dgsend(obj, typeArgs, method, @rest args) =>
     _callMethod(obj, method, typeArgs, args, method);
 
-dindex(obj, index) => _callMethod(obj, '_get', null, JS('', '[#]', index), '[]');
+dindex(obj, index) =>
+    _callMethod(obj, '_get', null, JS('', '[#]', index), '[]');
 
 dsetindex(obj, index, value) =>
     _callMethod(obj, '_set', null, JS('', '[#, #]', index, value), '[]=');
 
 /// TODO(leafp): This duplicates code in types.dart.
 /// I haven't found a way to factor it out that makes the
 /// code generator happy though.
 _ignoreMemo(f) => JS(
     '',
     '''(() => {
@@ skipping 213 matching lines @@
     }
   } else if (typeof $values === 'object') {
     for (let key of $getOwnPropertyNames($values)) {
       map._set(key, $values[key]);
     }
   }
   return map;
 })()''');
 
 @JSExportName('assert')
-assert_(condition) => JS(
+assert_(condition, [message]) => JS(
     '',
     '''(() => {
-  if (!$condition) $throwAssertionError();
+  if (!$condition) $throwAssertionError(message);
 })()''');
 
 var _stack = null;
 @JSExportName('throw')
 throw_(obj) => JS(
     '',
     '''(() => {
     $_stack = new Error();
     throw $obj;
 })()''');
@@ skipping 277 matching lines @@
     name = '+' + name;
   }
   return name;
 }
 
 /// Emulates the implicit "loadLibrary" function provided by a deferred library.
 ///
 /// Libraries are not actually deferred in DDC, so this just returns a future
 /// that completes immediately.
 Future loadLibrary() => new Future.value();