include shared-styles

Change-Id: I74abedbc5874152565af900c9f11a5feae4db1a9
diff --git a/gr-image-diff-tool/gr-image-diff-tool_html.js b/gr-image-diff-tool/gr-image-diff-tool_html.js
index 6a25ff5..887a028 100644
--- a/gr-image-diff-tool/gr-image-diff-tool_html.js
+++ b/gr-image-diff-tool/gr-image-diff-tool_html.js
@@ -16,7 +16,7 @@
  */
 
 export const htmlTemplate = Polymer.html`
-<style>
+<style include="shared-styles">
   :host {
     background-color: var(--table-header-background-color, #fafafa);
     display: block;