Fix an incorrect variable name in pdf_viewer.js.

Change-Id: If4d8aff0ccf0c314424b53310de63bbe06c526d9
Reviewed-on: https://chromium-review.googlesource.com/c/1460446
Reviewed-by: dstockwell <dstockwell@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630370}
1 file changed