MD User Manager: fix <paper-checkbox> ripple sizes

R=mahmadi@chromium.org
BUG=645417
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2339353002
Cr-Commit-Position: refs/heads/master@{#419194}

chrome/browser/resources/md_user_manager/user_manager.html

@@ -27,6 +27,7 @@
   <!-- Make sure iron-icon and cr iconset are imported to use in
        user_pod_template.html -->
   <link rel="import" href="chrome://resources/cr_elements/icons.html">
+  <link rel="import" href="chrome://resources/cr_elements/shared_vars_css.html">
   <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
   <!-- Make sure paper-button is imported to use in user_pod_template.html -->
   <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">