Fixed bug where PlzNavigate CSP in a iframe did not get the inherited CSP

When inheriting the CSP from a parent document to a local-scheme CSP,
it does not always get propagated to the PlzNavigate CSP. This means
that PlzNavigate CSP checks (like `frame-src`) would be ran against
a blank policy instead of the proper inherited policy.

Bug: 778658
Change-Id: I61bb0d432e1cea52f199e855624cb7b3078f56a9
Reviewed-on: https://chromium-review.googlesource.com/765969
Commit-Queue: Andy Paicu <andypaicu@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#518245}
AXObjectCache* Document::GetOrCreateAXObjectCache() const {
  Settings* settings = GetSettings();
  if (!settings || !settings->GetAccessibilityEnabled())
    return nullptr;

  Document& cache_owner = AXObjectCacheOwner();

  if (!cache_owner.GetLayoutView())
    return nullptr;

  DCHECK(&cache_owner == this || !ax_object_cache_);
  if (!cache_owner.ax_object_cache_)
    cache_owner.ax_object_cache_ = AXObjectCache::Create(cache_owner);
  return cache_owner.ax_object_cache_.Get();
}

AXObjectCache* Document::GetOrCreateAXObjectCache() const {
  Settings* settings = GetSettings();
  if (!settings || !settings->GetAccessibilityEnabled())
    return nullptr;

  Document& cache_owner = AXObjectCacheOwner();

  if (!cache_owner.GetLayoutView())
    return nullptr;

  DCHECK(&cache_owner == this || !ax_object_cache_);
  if (!cache_owner.ax_object_cache_)
    cache_owner.ax_object_cache_ = AXObjectCache::Create(cache_owner);
  return cache_owner.ax_object_cache_.Get();
}
