CLJS-2166: Add uri? predicate

Clojure introduced a `uri?` predicate in 1.9. This commit adds support for `uri`
to Clojurescript under `cljs.core/uri?`. It returns true if the given argument
is an instance of `goog.Uri`, false otherwise.

Author: lxsameer

src/main/cljs/cljs/core.cljs

@@ -11,7 +11,8 @@
             goog.math.Integer
             [goog.string :as gstring]
             [goog.object :as gobject]
-            [goog.array :as garray])
+            [goog.array :as garray]
+            [goog.Uri])
   (:import [goog.string StringBuffer]))
 
 ;; next line is auto-generated by the build-script - Do not edit!
@@ -11166,3 +11167,9 @@ reduces them without incurring seq initialization"
   Bootstrap only."
   [ns-obj]
   (.-name ns-obj))
+
+(defn uri?
+  "Returns true X is a goog.Uri instance."
+  {:added "1.9"}
+  [x]
+  (instance? goog.Uri x))

src/test/cljs/cljs/core_test.cljs

@@ -1492,3 +1492,13 @@
   ;;   (assert (= (:arglists var-meta) '([a b]))))
 
   )
+
+(deftest uri-predicate
+  (testing "Testing uri?"
+    (is (not (uri? "http://clojurescript.org")))
+    (is (not (uri? 42)))
+    (is (not (uri? [])))
+    (is (not (uri? {})))
+    (is (uri? (goog.Uri. "")))
+    (is (uri? (goog.Uri. "http://clojurescript.org")))
+    (is (uri? (goog.Uri. "some string")))))