Updating trunk VERSION from 3387.0 to 3388.0

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

Change-Id: I6cc15c09a93ea06cb91a64a624ecc9d25226642d
Reviewed-on: https://chromium-review.googlesource.com/991573Reviewed-by: chrome-release-bot@chromium.org <chrome-release-bot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547611}

chrome/VERSION

 MAJOR=67
 MINOR=0
-BUILD=3387
+BUILD=3388
 PATCH=0