appengine: add low latency publish comment (GoogleCloudPlatform#2264)

* appengine: add low latency publish comment

* nit: remove trailing space

* nit: remove spaces

Author: anguillanneuf

appengine/flexible/pubsub/main.py

@@ -44,6 +44,8 @@ def index():
 
     data = request.form.get('payload', 'Example payload').encode('utf-8')
 
+    # Consider initialzing the publisher client outside this function
+    # for low latency publish.
     publisher = pubsub_v1.PublisherClient()
     topic_path = publisher.topic_path(
         current_app.config['PROJECT'],