If you have a Chromebook, this gives you speech support built-in. If you're building Chrome from source and running it on desktop Linux, speech won't be included by default. Here's how to enable it.
Add chromeos=1 to your GYP_DEFINES. (More info on GYP_DEFINES here)
Now build Chrome as usual, e.g.:
And run it as usual to see a mostly-complete Chrome OS desktop inside of a window:
By default you'll be logged in as the default user. If you want to simulate the login manager too, run it like this:
If you want speech, you just need to copy the speech synthesis data files to /usr/share like it would be on a Chrome OS device:
After you do that, just run "chrome" as above (e.g. out/Release/chrome) and press Ctrl+Alt+Z, and you should hear it speak! If not, check the logs.
For more information on how to develop and debug ChromeVox, see ChromeVox (for developers).