tag Node.js vars as 'js to avoid .call invokes

Author: swannodette

src/main/clojure/cljs/analyzer.cljc

@@ -1073,7 +1073,8 @@
   [env sym full-ns current-ns]
   {:name (symbol (str current-ns) (str (munge-node-lib full-ns) "." (name sym)))
    :op :js-var
-   :ns current-ns})
+   :ns current-ns
+   :tag 'js})
 
 (defmethod resolve* :global
   [env sym full-ns current-ns]

src/main/clojure/cljs/compiler.cljc

@@ -1142,7 +1142,7 @@
         opt-count? (and (= (:name info) 'cljs.core/count)
                         (boolean ('#{string array} first-arg-tag)))
         ns (:ns info)
-        js? (or (= ns 'js) (= ns 'Math))
+        js? (or (= ns 'js) (= ns 'Math) (= tag 'js))
         goog? (when ns
                 (or (= ns 'goog)
                     (when-let [ns-str (str ns)]