Spelling corrections to the API header file

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index 08d010401976161223ec1bc91c8c59e88473e797..b282bf2fd913c338eba9f83747b290160c139391 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -690,11 +690,11 @@ DART_EXPORT bool Dart_PostIntArray(Dart_Port port_id,
 }
 
 
-DART_EXPORT bool Dart_PostCObject(Dart_Port port_id, Dart_CObject* root) {
+DART_EXPORT bool Dart_PostCObject(Dart_Port port_id, Dart_CObject* message) {
   uint8_t* buffer = NULL;
   MessageWriter writer(&buffer, allocator);
 
-  writer.WriteCMessage(root);
+  writer.WriteCMessage(message);
 
   // Post the message at the given port.
   return PortMap::PostMessage(new Message(