When creating the buffer for the fall back, the initial entry was not
considered when calculating the size.

Bug: chromium:896181
Change-Id: I7f15bb1bdf31b3255db91b1fe8dcd68c76033980
Reviewed-on: https://chromium-review.googlesource.com/c/1286957Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Peter Wong <peter.wm.wong@gmail.com>
Cr-Commit-Position: refs/heads/master@{#56768}