WebView 删除 cookies
NSHTTPCookie *cookie;
NSHTTPCookieStorage *cookieJar = [NSHTTPCookieStorage sharedHTTPCookieStorage];
NSArray *cookieAry = [cookieJar cookiesForURL: [NSURL URLWithString: @"http://api.m.taobao.com"]];
for (cookie in cookieAry) {
[cookieJar deleteCookie: cookie];
}