jscript: Implement WeakMap.clear().

dlls/jscript/set.c

@@ -669,8 +669,20 @@ void remove_weakmap_entry(struct weakmap_entry *entry)
 static HRESULT WeakMap_clear(script_ctx_t *ctx, jsval_t vthis, WORD flags, unsigned argc, jsval_t *argv,
         jsval_t *r)
 {
-    FIXME("\n");
-    return E_NOTIMPL;
+    WeakMapInstance *weakmap;
+    HRESULT hres;
+
+    hres = get_weakmap_this(ctx, vthis, &weakmap);
+    if(FAILED(hres))
+        return hres;
+
+    TRACE("%p\n", weakmap);
+
+    while(weakmap->map.root)
+        remove_weakmap_entry(RB_ENTRY_VALUE(weakmap->map.root, struct weakmap_entry, entry));
+
+    if(r) *r = jsval_undefined();
+    return S_OK;
 }
 
 static HRESULT WeakMap_delete(script_ctx_t *ctx, jsval_t vthis, WORD flags, unsigned argc, jsval_t *argv,