WebUI: cr-button, add missing import

Bug: 967793
Change-Id: I70a3b5e9451dbf9dbbd79a3fe6d7371adf9e9666
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1641366
Commit-Queue: Esmael El-Moslimany <aee@chromium.org>
Auto-Submit: Esmael El-Moslimany <aee@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665714}

ui/webui/resources/cr_elements/cr_button/BUILD.gn

@@ -13,6 +13,7 @@ js_type_check("closure_compile") {
 js_library("cr_button") {
   deps = [
     "//third_party/polymer/v1_0/components-chromium/paper-behaviors:paper-ripple-behavior-extracted",
+    "//ui/webui/resources/js:cr",
     "//ui/webui/resources/js/cr/ui:focus_outline_manager",
   ]
 }

ui/webui/resources/cr_elements/cr_button/cr_button.html

 <link rel="import" href="../../html/polymer.html">
 
+<link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/cr/ui/focus_outline_manager.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-behaviors/paper-ripple-behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/color.html">