Description:

When I type a message that spans several lines, Rocket.Chat becomes very sluggish.

Server Setup Information:

• Version of Rocket.Chat Server: 0.63.2
• Operating System: Debian stretch
• Deployment Method(snap/docker/tar/etc): tar
• Number of Running Instances: 1
• DB Replicaset Oplog: Disabled
• Node Version: v8.9.3
• mongoDB Version: mongodb-org 3.2.17

Steps to Reproduce:

1. Type several lines into the message box (separate the lines with Shift+Enter). The lines don't have to be long - ten lines with a single character will trigger the issue just fine:

   a
   a
   a
   a
   a
   a
   a
   a
   a
   

   More lines seem to increase the sluggishness.

2. Now try to type a complete sentence, e.g. The quick brown fox jumps over the lazy dog. Notice how sluggish the typing has become.

I can reproduce this issue both in the Electron client on Ubuntu, and on the website.

Expected behavior:

Typing shouldn't slow down just because of a few lines.

Actual behavior:

Typing slows down noticeably.