Added WeakSet constructor

src/js.rs

@@ -619,6 +619,17 @@ extern {
     pub fn delete(this: &WeakMap, key: Object) -> bool;
 }
 
+#[wasm_bindgen]
+extern {
+    pub type WeakSet;
+
+    /// The WeakSet object lets you store weakly held objects in a collection.
+    /// 
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet
+    #[wasm_bindgen(constructor)]
+    pub fn new() -> WeakSet;
+}
+
 // JsString
 #[wasm_bindgen]
 extern {

tests/all/js_globals/WeakSet.rs

@@ -0,0 +1,29 @@
+#![allow(non_snake_case)]
+
+use project;
+
+#[test]
+fn new() {
+    project()
+        .file("src/lib.rs", r#"
+            #![feature(proc_macro, wasm_custom_section)]
+
+            extern crate wasm_bindgen;
+            use wasm_bindgen::prelude::*;
+            use wasm_bindgen::js;
+
+            #[wasm_bindgen]
+            pub fn new_weak_set() -> js::WeakSet {
+                js::WeakSet::new()
+            }
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                assert.equal(typeof wasm.new_weak_set(), "object");
+            }
+        "#)
+        .test()
+}

tests/all/js_globals/mod.rs

@@ -9,6 +9,7 @@ mod Function;
 mod JsString;
 mod Math;
 mod WeakMap;
+mod WeakSet;
 mod Number;
 mod Object;
 mod TypedArray;