narrow [nfc]: Inline showStreamInHomeNarrow

For an upcoming change to this logic, we'll want the call site
to have its hands on the Subscription object.

Author: gnprice

src/chat/narrowsSelectors.js

@@ -87,22 +87,6 @@ export const getMessagesForNarrow: Selector<$ReadOnlyArray<Message | Outbox>, Na
     },
   );
 
-/** Whether this stream's messages should appear in the "all messages" narrow. */
-const showStreamInHomeNarrow = (
-  streamId: number,
-  subscriptions: Map<number, Subscription>,
-): boolean => {
-  const sub = subscriptions.get(streamId);
-  if (!sub) {
-    // If there's no matching subscription, then the user must have
-    // unsubscribed from the stream since the message was received.  Leave
-    // those messages out of this view, just like for a muted stream.
-    return false;
-  }
-
-  return sub.in_home_view;
-};
-
 /**
  * The known messages that should appear in the given narrow's message list.
  *
@@ -128,8 +112,15 @@ export const getShownMessagesForNarrow: Selector<$ReadOnlyArray<Message | Outbox
             if (flags.mentioned[message.id]) {
               return true;
             }
+            const sub = subscriptions.get(message.stream_id);
+            if (!sub) {
+              // If there's no matching subscription, then the user must have
+              // unsubscribed from the stream since the message was received.  Leave
+              // those messages out of this view, just like for a muted stream.
+              return false;
+            }
             return (
-              showStreamInHomeNarrow(message.stream_id, subscriptions)
+              sub.in_home_view
               && !isTopicMuted(message.stream_id, message.subject, mute)
             );
           }),