Makes the script a bit more accurate in identifying place-holder
header files.
Bug: None
Change-Id: Iba13562aed0d40bffef9c25d7345f3bb8af16c29
No-Try: true
Reviewed-on: https://webrtc-review.googlesource.com/4381
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20357}