The jsapi-harness test runs the JS-API spec tests of WebAssembly, which
get fetched from github when 'gclient sync' is executed. Without
'gclient sync' the harness may executed a version of the tests which is
older than required by the harness. In this CL I add a suggestion to
the test to run 'gclient sync' which is shown when the test is failing.

R=marja@chromium.org

Change-Id: I36d03bebc4d6cc554eefd4eb376c3d309b7ee5b9
Reviewed-on: https://chromium-review.googlesource.com/558419Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46375}