Updating trunk VERSION from 3399.0 to 3400.0

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

Change-Id: I7a6584f1fe637a58c913650928a0e224d3d48b4a
Reviewed-on: https://chromium-review.googlesource.com/1015335Reviewed-by: chrome-release-bot@chromium.org <chrome-release-bot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551565}

chrome/VERSION

 MAJOR=68
 MINOR=0
-BUILD=3399
+BUILD=3400
 PATCH=0