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 Document::setXMLVersion(const String& version,
                             ExceptionState& exception_state) {
  if (!XMLDocumentParser::SupportsXMLVersion(version)) {
    exception_state.ThrowDOMException(
        kNotSupportedError,
        "This document does not support the XML version '" + version + "'.");
    return;
  }

  xml_version_ = version;
}

void Document::setXMLVersion(const String& version,
                             ExceptionState& exception_state) {
  if (!XMLDocumentParser::SupportsXMLVersion(version)) {
    exception_state.ThrowDOMException(
        kNotSupportedError,
        "This document does not support the XML version '" + version + "'.");
    return;
  }

  xml_version_ = version;
}
