Google added to Chromium 43.x a new addon called "Chrome Hotword Shared Module" without source code. At first run is automatically downloaded and installed without any prompt. After this installation is only available at chrome://voicesearch/ and is not shown in the extensions menu and by default the user is not able to disable or unistall it. This addon can record audio anytime since is linked to the Ok Google feature ( https://support.google.com/websearch/answer/2940021?hl=en [google.com] [support.google.com] ).
Sources:
https://code.google.com/p/chromium/issues/detail?id=500922 [google.com]
http://www.ghacks.net/2015/06/19/googles-in-hot-water-after-dropping-binary-code-in-chromium-for-linux/ [ghacks.net]