Re-land else-after-returns

Revert "Revert "Fix else-after-returns throughout pdfium.""
This reverts commit 4eb4d7f6c707cc2c23c806aa540d055c8832b55d.

Fix one naming conflict.

TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/1243953004 .
78 files changed