Updating trunk VERSION from 3406.0 to 3407.0

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

Change-Id: I78da3580d059c4e8a5ff447220917b175eaa7010
Reviewed-on: https://chromium-review.googlesource.com/1027310Reviewed-by: chrome-release-bot@chromium.org <chrome-release-bot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553439}

chrome/VERSION

 MAJOR=68
 MINOR=0
-BUILD=3406
+BUILD=3407
 PATCH=0