headless: Add a dummy include for version.h

Add a dummy include for the generated version.h to make sure it will
always be available for users of the headless API.

BUG=546953
TBR=altimin@chromium.org

Review-Url: https://codereview.chromium.org/2708643003
Cr-Commit-Position: refs/heads/master@{#451595}
1 file changed