Revert deprecation of webkitURL on Window

Intent thread:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/EEo3kba4h2g

Bug: 348985
Change-Id: Ia35a1075aca6a2a82de22bda737cb92885453d11
Reviewed-on: https://chromium-review.googlesource.com/c/1334987
Commit-Queue: Philip J├Ągenstedt <foolip@chromium.org>
Reviewed-by: Philip J├Ągenstedt <foolip@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607968}
13 files changed