Disallow access to opaque CSS responses.

Bug: 848786
Change-Id: Ie53fbf644afdd76d7c65649a05c939c63d89b4ec
Reviewed-on: https://chromium-review.googlesource.com/1088335
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565537}
static bool IsAcceptableCSSStyleSheetParent(const Node& parent_node) {
  return parent_node.IsDocumentNode() || IsHTMLLinkElement(parent_node) ||
         IsHTMLStyleElement(parent_node) || IsSVGStyleElement(parent_node) ||
         parent_node.getNodeType() == Node::kProcessingInstructionNode;
}

static bool IsAcceptableCSSStyleSheetParent(const Node& parent_node) {
  return parent_node.IsDocumentNode() || IsHTMLLinkElement(parent_node) ||
         IsHTMLStyleElement(parent_node) || IsSVGStyleElement(parent_node) ||
         parent_node.getNodeType() == Node::kProcessingInstructionNode;
}
