In April, Google added the ability to share your screen with a Google AdWords support representation. Now, Google is adding video calls, over the same technology they use for Google+ Hangouts.
Google announced this in the Google AdWords Help community. You can access this help between the support hours by going to your AdWords account and clicking on Help on the top right. Then under the Contact us menu you may see the "Video Call" option:
Then it will open up a new window, like the Google Hangouts, that looks like this:
Forum discussion at Google AdWords Help.