Chrome: 54.0.2840.99 m
Windows: 10.0.105.86 Build 10586

Repro steps:
1. Turn on Chromevox on Chrome.
2. make Chromevox inactive.
3. Open Hangouts Chrome extension or open hangouts.google.com on Chrome.
4. make a chat conversation and receive a message.
Actual: Chromevox reads the chat contents.
Expected: Chromevox should read nothing when it is inactive.