On Chrome OS, you can enable spoken feedback (ChromeVox) by pressing Ctrl+Alt+Z.
To test the version of ChromeVox that runs on Chrome OS while running a desktop Linux build of Chrome with the chromeos=1 GYP flag, you just need to copy the speech synthesis data filesto /usr/share like it would be on a Chrome OS device:
git clone https://chromium.googlesource.com/chromiumos/platform/assets
sudo mv assets /usr/share/chromeos-assets
for f in *.zip; do sudo unzip $f && rm $f; done
After you do that, just run "chrome" and press Ctrl+Alt+Z and you should hear it speak! If not, check the logs.