Add is<T> to IRNode types.

This is a shorthand function for verifying the kind of IRNode you have.

Change-Id: Ifc53100b6d29d9fcd02e90e0658fda971f136210
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/315256
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
4 files changed