DevTools: mark http/tests/inspector/console-xhr-logging.html as slow on Release

BUG=
TBR= yurys@chromium.org

Review URL: https://codereview.chromium.org/677953003

git-svn-id: svn://svn.chromium.org/blink/trunk@184459 bbb929c8-8fbe-4397-9dbb-9b2b20218538