Move Pepper-specific Linux font code from pdf/pdfium/ to
pdf/ppapi_migration/. In pdf/pdfium/, start using
blink::WebFontDescription in place of pp::BrowserFontDescription. In
pdf/ppapi_migration/, translate blink::WebFontDescription to
pp::BrowserFontDescription.
Bug: 1139079
Change-Id: Ie5e8fa1bb1e06c73ed0ee28f848ead90ec7d0523
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2853426
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Reviewed-by: K. Moon <kmoon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#886555}