Replacing the lock icon with a neutral indicator prevents the misunderstanding that the lock icon is associated with the trustworthiness of a page, and emphasizes that security should be the default state in Chrome. Our research has also shown that many users never understood that clicking the lock icon showed important information and controls. We think the new icon helps make permission controls and additional security information more accessible, while avoiding the misunderstandings that plague the lock icon.
Explanation why Chrome lock icon was replaced with tune icon