Updating trunk VERSION from 4256.0 to 4257.0

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

Change-Id: I831e2a13dce08f1dacdd4969dd5c84208723ca20
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2394200Reviewed-by: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#804621}

chrome/VERSION

 MAJOR=87
 MINOR=0
-BUILD=4256
+BUILD=4257
 PATCH=0