Prevent sandboxed documents from reusing the default window

Bug: 377995
Change-Id: Iff66c6d214dfd0cb7ea9c80f83afeedfff703541
Reviewed-on: https://chromium-review.googlesource.com/983558
Commit-Queue: Andy Paicu <andypaicu@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567663}
WebPluginContainerImpl* LocalFrame::GetWebPluginContainer(Node* node) const {
  if (GetDocument() && GetDocument()->IsPluginDocument()) {
    return ToPluginDocument(GetDocument())->GetPluginView();
  }
  if (!node) {
    DCHECK(GetDocument());
    node = GetDocument()->FocusedElement();
  }

  if (node) {
    return node->GetWebPluginContainer();
  }
  return nullptr;
}

WebPluginContainerImpl* LocalFrame::GetWebPluginContainer(Node* node) const {
  if (GetDocument() && GetDocument()->IsPluginDocument()) {
    return ToPluginDocument(GetDocument())->GetPluginView();
  }
  if (!node) {
    DCHECK(GetDocument());
    node = GetDocument()->FocusedElement();
  }

  if (node) {
    return node->GetWebPluginContainer();
  }
  return nullptr;
}
