clang-format all pdfium code, again.

Also add a presubmit that checks for this so I don't have to keep doing it.
No behavior change.

Generated by:
  find . -name '*.cpp' -o -name '*.h' | \
  grep -E -v 'third_party|thirdparties|lpng_v163' | \
  xargs ../../buildtools/mac/clang-format -i

BUG=none
R=thestig@chromium.org

Review URL: https://codereview.chromium.org/1272653005 .
15 files changed