Merge to XFA: Return error information from pdfium to JS.

Cherry-pick from b720d0a14601f1496ef15297bc46d401f5a2a890 +
Manually resolve merge conflicts +
Fix more IWYU to fix compile.

Original Review URL: https://codereview.chromium.org/963193003
TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/971013002
14 files changed