GitLab

Specifically
 - Converting PDFScriptingAPI, PDFViewer, ViewportScroller classes.
 - Fixing newly revealed type errors (only happening with classes
   which are @struct by default).

Bug: 1005029
Change-Id: I15490634db5c3e3c395facc4e57b4106eab3b494
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1820101
Auto-Submit: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699162}