Add Dart_GetNativeArgumentCount() and a test.

runtime/vm/dart_api_impl.cc

 // Copyright (c) 2011, 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.
 
 #include "include/dart_api.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
 #include "vm/dart.h"
@@ skipping 1139 matching lines @@
 DART_EXPORT Dart_Handle Dart_GetNativeArgument(Dart_NativeArguments args,
                                                int index) {
   Zone zone;  // Setup a VM zone as we are creating some handles.
   HandleScope scope;  // Setup a VM handle scope.
   NativeArguments* arguments = reinterpret_cast<NativeArguments*>(args);
   const Object& obj = Object::Handle(arguments->At(index));
   return Api::NewLocalHandle(obj);
 }
 
 
+DART_EXPORT int Dart_GetNativeArgumentCount(Dart_NativeArguments args) {
+  NativeArguments* arguments = reinterpret_cast<NativeArguments*>(args);
+  return arguments->Count();
+}
+
+
 DART_EXPORT void Dart_SetReturnValue(Dart_NativeArguments args,
                                      Dart_Handle retval) {
   Zone zone;  // Setup a VM zone as we are creating some handles.
   HandleScope scope;  // Setup a VM handle scope.
   NativeArguments* arguments = reinterpret_cast<NativeArguments*>(args);
   arguments->SetReturn(Object::Handle(Api::UnwrapHandle(retval)));
 }
 
 
 DART_EXPORT bool Dart_ExceptionOccurred(Dart_Handle result) {
@@ skipping 551 matching lines @@
   ASSERT(isolate != NULL);
   ApiState* state = isolate->api_state();
   ASSERT(state != NULL);
   ApiLocalScope* scope = state->top_scope();
   ASSERT(scope != NULL);
   return scope->zone().Reallocate(ptr, old_size, new_size);
 }
 
 
 }  // namespace dart