Remove strange function overloading

Removing this behavior caused one test to fail, and the test was sending an array to a function
which expected a string.

I did some light live testing and didn't notice any breakage.

Author: philc

background_scripts/completion_engines.js

@@ -40,7 +40,7 @@ class BaseEngine {
     return Utils.matchesAnyRegexp(this.regexps, searchUrl);
   }
   getUrl(queryTerms) {
-    return UrlUtils.createSearchUrl(queryTerms, this.engineUrl);
+    return UrlUtils.createSearchUrl(queryTerms.join(" "), this.engineUrl);
   }
 }
 

lib/url_utils.js

@@ -127,15 +127,10 @@ const UrlUtils = {
     return searchUrl.replace(/%s/g, this.createSearchQuery(query));
   },
 
-  // Map a search query to its URL encoded form. The query may be either a string or an array of
-  // strings. E.g. "BBC Sport" -> "BBC%20Sport".
-  // TODO(philc): Why do we allow both a string and array as arguments? Let's pick one and change
-  // the callers.
+  // Map a search query to its URL encoded form. E.g. "BBC Sport" -> "BBC%20Sport".
   createSearchQuery(query) {
-    if (typeof query === "string") {
-      query = query.split(/\s+/);
-    }
-    return query.map(encodeURIComponent).join("%20");
+    const parts = query.split(/\s+/);
+    return parts.map(encodeURIComponent).join("%20");
   },
 };