Reminder: test with new Tint SPIRV reader #189

From the Dawn chat:

If you're using the Tint SPIR-V reader, the IR reader is very close to being complete. We'll start wider testing soon, and if our tests don't find any issues we'll swap over and delete the AST reader. So, if you're using it, please file bugs at http://crbug.com/dawn if you have any IR reader issues so we can fix them before swapping.