Reland of Add PDFium build_overrides

This reverts commit e43a2442a5e5e1000021caf9f692b69208e1e53c.

This CL adds the build override settings so we can enable XFA in GN builds
in the future.

BUG=chromium:62400

Review-Url: https://codereview.chromium.org/1937273002
Cr-Commit-Position: refs/heads/master@{#391227}
2 files changed