It seems CEF lacks support for the Speech API.
The Google Speech Demo:
https://www.google.com/intl/en/chrome/demos/speech.html
Here are three tests that work in the Chrome browser, but not in CEF.
Demo 01 Unity Speech Dictation: https://theylovegames.com/UnityWebGLSpe ... Dictation/
Demo 02 Unity Speech Commands: https://theylovegames.com/UnityWebGLSpe ... hCommands/
Demo 01 Unity Speech Synthesis: https://theylovegames.com/UnityWebGLSpe ... 1Synthesis