Merge branch 'jl-update-ff-process-docs' into 'master'

Add guidance for the initial state of a feature flag

See merge request gitlab-org/gitlab-ce!24829

PROCESS.md

@@ -110,6 +110,18 @@ picked into the stable branches) up to the 19th of the month. Such merge
 requests should have the ~"feature flag" label assigned, and don't require a
 corresponding exception request to be created. 
 
+A level of common sense should be applied when deciding whether to have a feature 
+behind a feature flag off or on by default.
+
+The following guideliness can be applied to help make this decision:
+
+* If the feature is not fully ready or functioning, the feature flag should be disabled by default.
+* If the feature is ready but there are concerns about performance or impact, the feature flag should be enabled by default, but 
+disabled via chatops before deployment on GitLab.com environments. If the performance concern is confirmed, the final release should have the feature flag disabled by default.
+* In most other cases, the feature flag can be enabled by default.
+
+For more information on rolling out changes using feature flags, read [through the documentation](https://docs.gitlab.com/ee/development/rolling_out_changes_using_feature_flags.html).
+
 In order to build the final package and present the feature for self-hosted
 customers, the feature flag should be removed. This should happen before the
 22nd, ideally _at least_ 2 days before. That means MRs with feature