Same problem: Chromium 28 and no webapps integration. In Firefox webapps works ok.
Starting chromium-browser from terminal, I saw this warning:
** (exe:9416): WARNING **: Failed to find domain member of JSON manifest
And I found that was caused by the Google Plus webapps, that does not declare a domain in JSON manifest; so uninstalled it and tried again: no more warning but still no integration.
Same problem: Chromium 28 and no webapps integration. In Firefox webapps works ok.
Starting chromium-browser from terminal, I saw this warning:
** (exe:9416): WARNING **: Failed to find domain member of JSON manifest
And I found that was caused by the Google Plus webapps, that does not declare a domain in JSON manifest; so uninstalled it and tried again: no more warning but still no integration.