Renable Gerrit, rules_gwt, TensorFlow in downstream (#737)
Renable Gerrit, rules_gwt, TensorFlow in downstream (#737)

They are all green with Bazel@HEAD
https://buildkite.com/bazel/bazel-at-head-plus-disabled/builds/223
bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration