Updating trunk VERSION from 3900.0 to 3901.0

# This is an automated release commit.
# Do not revert without consulting chrome-pmo@google.com.
NOAUTOREVERT=true
TBR=kariah@chromium.org

Change-Id: Ifa5a9b6e9d372d69a1f617ce6baaad8c5dd6d408
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1778970Reviewed-by: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#692375}

chrome/VERSION

 MAJOR=78
 MINOR=0
-BUILD=3900
+BUILD=3901
 PATCH=0