service worker: Disable interception when OBJECT/EMBED uses ImageLoader.

Per the specification, service worker should not intercept requests for
OBJECT/EMBED elements.

R=kinuko

Bug: 771933
Change-Id: Ia6da6107dc5c68aa2c2efffde14bd2c51251fbd4
Reviewed-on: https://chromium-review.googlesource.com/927303
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#538027}
void ImageLoader::DecodeRequest::ProcessForTask() {
  if (!loader_)
    return;

  DCHECK_EQ(state_, kPendingMicrotask);
  state_ = kPendingLoad;
  loader_->DispatchDecodeRequestsIfComplete();
}

void ImageLoader::DecodeRequest::ProcessForTask() {
  if (!loader_)
    return;

  DCHECK_EQ(state_, kPendingMicrotask);
  state_ = kPendingLoad;
  loader_->DispatchDecodeRequestsIfComplete();
}
