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- window.open's second argument is the context; in this case, we don't have one.
- Polymer recommends wrapping a paper-button with an anchor when treating the button like a link.
- s/options_page/optionsPage

Test: load an engine with a options page. Ensure it shows up and opens that page when clicked.
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I4210d6c306e2392841fdd9b9fb90ea1ab5c6ffb3
Reviewed-on: https://chromium-review.googlesource.com/1040679Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Reviewed-by: Katie Dektar <katie@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556277}