Don't remove -Wheader-hygiene for pdfium, 41f0590a9d7 fixed all violations.
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-rw-r--r-- 1553 LICENSE
-rw-r--r-- 507 codereview.settings
drwxr-xr-x - core
drwxr-xr-x - fpdfsdk
-rw-r--r-- 36823 pdfium.gyp