GitLab

Add a variant of CallPDFiumWideStringBufferApi() that distinguishes
between API call failure and empty string return values.

Change-Id: I4ec2c1ed16f9109854493f184acd597c8b622196
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2322167Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792454}