When Google+ came update 7.0, the main change that everyone noticed – Auto Hide the bottom tab bar. However, after viewing a couple of lines of application code was found, indicating that the addition of Custom Tabs.
It seems that the function is already available for some users, but is likely due to server change. Thus, whenever you click on any link inside the Google+ app, instead of being redirected into Chrome, or any third-party browser that you use, the link will be loaded inside Google+.
Custom Tab load faster full Chrome browser, but they retain all browser data, including logins, auto-complete forms, and are just as safe as Chrome. The only drawback is that you can not open the link and return to reading the Google+ stream.
Considering Google love to test functions with just a few users, yet not many will be able to take advantage of Custom Tabs. But we hope that in the next update of all Google+ users will this function.