Updating trunk VERSION from 3397.0 to 3398.0

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

Change-Id: I1c497305cdc100ff275e2a51d170735b39c1608a
Reviewed-on: https://chromium-review.googlesource.com/1013417Reviewed-by: chrome-release-bot@chromium.org <chrome-release-bot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550870}

chrome/VERSION

 MAJOR=68
 MINOR=0
-BUILD=3397
+BUILD=3398
 PATCH=0