Verify that header values set from Blink don't contain '\n'.

Because that would be silly.

Bug: 845961
Change-Id: I69de2cb093a3629de63c48652c9499f7387b8334
Reviewed-on: https://chromium-review.googlesource.com/1109757
Commit-Queue: Mike West <mkwst@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570206}
  KURL RegisterMockedUrl(const std::string& url_root,
                         const WTF::String& filename) {
    WebURLResponse response;
    response.SetMIMEType("text/html");
    KURL url = ToKURL(url_root + filename.Utf8().data());
    Platform::Current()->GetURLLoaderMockFactory()->RegisterURL(
        url, response, test::CoreTestDataPath(filename.Utf8().data()));
    return url;
  }

  KURL RegisterMockedUrl(const std::string& url_root,
                         const WTF::String& filename) {
    WebURLResponse response;
    response.SetMIMEType("text/html");
    KURL url = ToKURL(url_root + filename.Utf8().data());
    Platform::Current()->GetURLLoaderMockFactory()->RegisterURL(
        url, response, test::CoreTestDataPath(filename.Utf8().data()));
    return url;
  }
