Inherit CSP when we inherit the security origin

This prevents attacks that use main window navigation to get out of the
existing csp constraints such as the related bug

Bug: 747847
Change-Id: I1e57b50da17f65d38088205b0a3c7c49ef2ae4d8
Reviewed-on: https://chromium-review.googlesource.com/592027
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Andy Paicu <andypaicu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#492333}
void DocumentLoader::CommitData(const char* bytes, size_t length) {
  EnsureWriter(response_.MimeType());
  DCHECK_GE(state_, kCommitted);

  if (!frame_ || !frame_->GetDocument()->Parsing())
    return;

  if (length)
    data_received_ = true;

  writer_->AddData(bytes, length);
}

void DocumentLoader::CommitData(const char* bytes, size_t length) {
  EnsureWriter(response_.MimeType());
  DCHECK_GE(state_, kCommitted);

  if (!frame_ || !frame_->GetDocument()->Parsing())
    return;

  if (length)
    data_received_ = true;

  writer_->AddData(bytes, length);
}
