The recent introduction of 'end' positions incorrectly tracked column
positions. This CL fixes that.

R=tebbi@chromium.org

Bug: v8:7793
Change-Id: I2170ebb2dda062c9842dad657c3c516e0550b459
Reviewed-on: https://chromium-review.googlesource.com/c/1482830Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59794}