--- a/devtools/client/inspector/rules/test/head.js
+++ b/devtools/client/inspector/rules/test/head.js
@@ -327,34 +327,16 @@ var waitForSuccess = Task.async(function
       ok(false, "Failure: " + desc);
       break;
     }
     yield new Promise(r => setTimeout(r, 200));
   }
 });
 
 /**
- * Create a new style tag containing the given style text and append it to the
- * document's head node
- *
- * @param {Document} doc
- * @param {String} style
- * @return {DOMNode} The newly created style node
- */
-function addStyle(doc, style) {
-  info("Adding a new style tag to the document with style content: " +
-    style.substring(0, 50));
-  let node = doc.createElement("style");
-  node.setAttribute("type", "text/css");
-  node.textContent = style;
-  doc.getElementsByTagName("head")[0].appendChild(node);
-  return node;
-}
-
-/**
  * Get the dataURL for the font family tooltip.
  *
  * @param {String} font
  *        The font family value.
  * @param {object} nodeFront
  *        The NodeActor that will used to retrieve the dataURL for the
  *        font family tooltip contents.
  */