Updating trunk VERSION from 3419.0 to 3420.0

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

Change-Id: Ia7712f84414c21690e9ac5715d37fe8e90a9d557
Reviewed-on: https://chromium-review.googlesource.com/1043472Reviewed-by: chrome-release-bot@chromium.org <chrome-release-bot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555973}

chrome/VERSION

 MAJOR=68
 MINOR=0
-BUILD=3419
+BUILD=3420
 PATCH=0