Append slash to STATIC_RESOURCE_PATH

Needed to imitate the behavior of the regex extraction method.

Change-Id: I70e63e1e6607692cc9b6cff0b90f4a8400322308
diff --git a/polygerrit-ui/app/elements/shared/gr-lib-loader/gr-lib-loader.js b/polygerrit-ui/app/elements/shared/gr-lib-loader/gr-lib-loader.js
index 28ff45d..de92d8a 100644
--- a/polygerrit-ui/app/elements/shared/gr-lib-loader/gr-lib-loader.js
+++ b/polygerrit-ui/app/elements/shared/gr-lib-loader/gr-lib-loader.js
@@ -112,7 +112,9 @@
     _getLibRoot() {
       // TODO(wyatta): Remove the remainder of this method logic once the
       // STATIC_RESOURCE_PATH variable is being provided generally.
-      if (window.STATIC_RESOURCE_PATH) { return window.STATIC_RESOURCE_PATH; }
+      if (window.STATIC_RESOURCE_PATH) {
+        return window.STATIC_RESOURCE_PATH + '/';
+      }
 
       if (this._cachedLibRoot) { return this._cachedLibRoot; }