The Netscape Plug-in API is one of the older methods for extending the architecture and functionality of the browser. Google engineers say that the API has outlived its usefulness and is now a major cause of stability and security problems in Chrome. Eventually, that will mean that some plug-ins such as Google Earth, Microsoft Silverlight and others eventually will be blocked. Google also is planning to remove apps from the Chrome Web Store that use the API from the Web Store in January 2014, and then gradually remove all support for it over the next few months.
Source: https://threatpost.com/google-to-block-many-plug-ins-starting-in-2014/102393/