[wasm] Use correct bindings APIs

Use ScriptState::ForCurrentRealm in static methods, instead of
ForRelevantRealm().

Bug: chromium:788453
Change-Id: I63bd25e3f5a4e8d7cbaff945da8df0d71aa65527
Reviewed-on: https://chromium-review.googlesource.com/795096
Commit-Queue: Mircea Trofin <mtrofin@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520174}
  void Trace(blink::Visitor* visitor) {
    visitor->Trace(consumer_);
    visitor->Trace(client_);
    FetchDataLoader::Trace(visitor);
    BytesConsumer::Client::Trace(visitor);
  }

  void Trace(blink::Visitor* visitor) {
    visitor->Trace(consumer_);
    visitor->Trace(client_);
    FetchDataLoader::Trace(visitor);
    BytesConsumer::Client::Trace(visitor);
  }
