Revert "stream_wrap: reference handle before uv_write2"

It's segfaulting in release mode and asserting in debug mode:

  #
  # Fatal error in ../../deps/v8/src/api.h, line 297
  # CHECK(allow_empty_handle || that != __null) failed
  #

This reverts commit 99f0b02.

src/stream_wrap.cc

@@ -77,7 +77,6 @@ static Persistent<String> bytes_sym;
 static Persistent<String> write_queue_size_sym;
 static Persistent<String> onread_sym;
 static Persistent<String> oncomplete_sym;
-static Persistent<String> handle_sym;
 static SlabAllocator* slab_allocator;
 static bool initialized;
 
@@ -412,13 +411,6 @@ Handle<Value> StreamWrap::WriteStringImpl(const Arguments& args) {
       StreamWrap* send_stream_wrap = static_cast<StreamWrap*>(
           send_stream_obj->GetAlignedPointerFromInternalField(0));
       send_stream = send_stream_wrap->GetStream();
-
-      // Reference StreamWrap instance to prevent it from being garbage
-      // collected before `AfterWrite` is called.
-      if (handle_sym.IsEmpty()) {
-        handle_sym = NODE_PSYMBOL("handle");
-      }
-      req_wrap->object_->Set(handle_sym, send_stream_obj);
     }
 
     r = uv_write2(&req_wrap->req_,
@@ -476,9 +468,6 @@ void StreamWrap::AfterWrite(uv_write_t* req, int status) {
   assert(req_wrap->object_.IsEmpty() == false);
   assert(wrap->object_.IsEmpty() == false);
 
-  // Unref handle property
-  req_wrap->object_->Delete(handle_sym);
-
   if (status) {
     SetErrno(uv_last_error(uv_default_loop()));
   }