run clang-tidy on headers too

Without -header-filter='.*' clang-tidy only checks the .cpp file.

Change-Id: Ib49081faa2ddf20222dfeb15841cf2b812c22462
Reviewed-on: https://skia-review.googlesource.com/c/176967
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
2 files changed