This might be old news to you, but new to me:
In order to solve this problem, we decided to try to understand pages by executing JavaScript. It’s hard to do that at the scale of the current web, but we decided that it’s worth it. We have been gradually improving how we do this for some time. In the past few months, our indexing system has been rendering a substantial number of web pages more like an average user’s browser with JavaScript turned on.
I just ran into indexing of JavaScript that was embedded inside an iFrame. I figured no way they could index that, I was wrong.
Eric L. Barnes 