需要Chrome扩展程序帮助

Question

我试图让某个网站的某些元素按特定顺序点击，但我这样做有点麻烦。以下是我到目前为止的情况：

{
    "manifest_version": 2,

    "name":    "Test Extension",
    "version": "0.0",
    "offline_enabled": false,

    "content_scripts": [
      {
        "matches":    ["http://www.finishline.com/*", "https://www.finishline.com/*"],
        "js":         ["size.js"],
        "run_at":     "document_end",
        "all_frames": false
      }      

      {
        "matches":    ["http://www.finishline.com/*", "https://www.finishline.com/*"],
        "js":         ["content.js"],
        "run_at":     "document_end",
        "all_frames": false
      }
    ]
}

size.js：

document.getElementById('10').click();

content.js：

document.getElementById('buttonAddToCart').click();

以下是我希望此工作的示例页面（点击链接后我想将尺寸10添加到购物车中）：http://www.finishline.com/store/product?A=32440&categoryId=cat301568&productId=prod771501