fix optional params to mock methods, allow all signatures

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 74 matching lines @@
       return false;
     }
     if (!$instanceOfOrNull(opts[name], $type.named[name])) return false;
   }
   return true;
 })()''');
 
 Symbol _dartSymbol(name) =>
     JS('', '#(#.new(#.toString()))', const_, Symbol, name);
 
+/// Extracts the named argument array from a list of arguments, and returns it.
 // TODO(jmesserly): we need to handle named arguments better.
+extractNamedArgs(args) {
+  if (JS('bool', '#.length > 0', args)) {
+    var last = JS('', '#[#.length - 1]', args, args);
+    if (JS('bool', '# != null && #.__proto__ === Object.prototype',
+        last, last)) {
+      return JS('', '#.pop()', args);
+    }
+  }
+  return null;
+}
+
 _checkAndCall(f, ftype, obj, typeArgs, args, name) => JS('', '''(() => {
   $_trackCall($obj, $name);
 
   let originalTarget = obj === void 0 ? f : obj;
 
   function callNSM() {
-    let namedArgs = null;
-    if (args.length > 0 &&
-        args[args.length - 1].__proto__ == Object.prototype) {
-      namedArgs = args.pop();
-    }
     return $noSuchMethod(originalTarget, new $InvocationImpl(
-        $name, $args, {namedArguments: namedArgs, isMethod: true}));
+        $name, $args,
+        {namedArguments: $extractNamedArgs($args), isMethod: true}));
   }
   if (!($f instanceof Function)) {
     // We're not a function (and hence not a method either)
     // Grab the `call` method if it's not a function.
     if ($f != null) {
       $ftype = $getMethodType($f, 'call');
       $f = $f.call;
     }
     if (!($f instanceof Function)) {
       return callNSM();
@@ skipping 606 matching lines @@
   if (obj != null && getExtensionType(obj) != null) {
     return JS('', 'dartx.#', name);
   }
 
   // Check for certain names that we can't use in JS
   if (name == 'constructor' || name == 'prototype') {
     name = '+' + name;
   }
   return name;
 }