Inherit CSP when self-navigating to local-scheme URL

As the linked bug example shows, we should inherit CSP when we navigate
to a local-scheme URL (even if we are in a main browsing context).

Bug: 799747
Change-Id: I8413aa8e8049461ebcf0ffbf7b04c41d1340af02
Reviewed-on: https://chromium-review.googlesource.com/c/1234337
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Andy Paicu <andypaicu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597889}
DocumentInit DocumentInit::Create() {
  return DocumentInit(nullptr);
}

DocumentInit DocumentInit::Create() {
  return DocumentInit(nullptr);
}
