Make performance bar enabled checks consistent

Previously, we called the `peek_enabled?` method like so:

    prepend_before_action :set_peek_request_id, if: :peek_enabled?

Now we don't have a `set_peek_request_id` method, so we don't need that
line. However, the `peek_enabled?` part had a side-effect: it would also
populate the request store cache for whether the performance bar was
enabled for the current request or not.

This commit makes that side-effect explicit, and replaces all uses of
`peek_enabled?` with the more explicit
`Gitlab::PerformanceBar.enabled_for_request?`. There is one spec that
still sets `SafeRequestStore[:peek_enabled]` directly, because it is
contrasting behaviour with and without a request store enabled.

The upshot is:

1. We still set the value in one place. We make it more explicit that
   that's what we're doing.
2. Reading that value uses a consistent method so it's easier to find in
   future.

2 files changed, 2 insertions, 6 deletions

diff --git a/lib/peek/views/active_record.rb b/lib/peek/views/active_record.rb
index 2d78818630d..250c7d6aa8f 100644
--- a/lib/peek/views/active_record.rb
+++ b/lib/peek/views/active_record.rb
@@ -9,7 +9,7 @@ module Peek
         super
 
         subscribe('sql.active_record') do |_, start, finish, _, data|
-          if Gitlab::SafeRequestStore.store[:peek_enabled]
+          if Gitlab::PerformanceBar.enabled_for_request?
             unless data[:cached]
               detail_store << {
                 duration: finish - start,
diff --git a/lib/peek/views/redis_detailed.rb b/lib/peek/views/redis_detailed.rb
index f36f581d5e9..84041b6be73 100644
--- a/lib/peek/views/redis_detailed.rb
+++ b/lib/peek/views/redis_detailed.rb
@@ -16,7 +16,7 @@ module Gitlab
       private
 
       def add_call_details(duration, args)
-        return unless peek_enabled?
+        return unless Gitlab::PerformanceBar.enabled_for_request?
         # redis-rb passes an array (e.g. [:get, key])
         return unless args.length == 1
 
@@ -27,10 +27,6 @@ module Gitlab
         }
       end
 
-      def peek_enabled?
-        Gitlab::SafeRequestStore.store[:peek_enabled]
-      end
-
       def detail_store
         ::Gitlab::SafeRequestStore['redis_call_details'] ||= []
       end