You can see how rails is losing mindshare to newer frameworks.
I don't really think this proves anything. People who are already familiar with something aren't going to perform a vanilla Google search for it. For example, if I'm looking for a car, I'm not likely to perform a search for "automobile" but after overhearing somebody mention something called a Model S I might search for that.
A quick anecdote- I first learned about RoR circa 2008 from a colleague and performed a Google search for "Ruby on Rails" to find out what he was talking about. Fast forward three years and I was writing several web applications in it and don't recall ever performing that search again.
A far better metric I believe would be to perform an analysis of Stack Overflow questions by language and see whether it coincides with the chart the author cites.