WebUI: Add missing compress="gzip" attribute in certificate_shared_css.html.

Bug: 791195
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I129cfb90b0e0feb7fda89a431063fdd92de054d3
Reviewed-on: https://chromium-review.googlesource.com/804679Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521397}

ui/webui/resources/cr_components/cr_components_resources.grdp

@@ -78,7 +78,7 @@
     <structure name="IDR_WEBUI_CERTIFICATE_SHARED_CSS_HTML"
                file="cr_components/certificate_manager/certificate_shared_css.html"
                type="chrome_html"
-               preprocess="true" />
+               compress="gzip" />
     <structure name="IDR_WEBUI_CERTIFICATE_SUBENTRY_HTML"
                file="cr_components/certificate_manager/certificate_subentry.html"
                type="chrome_html"