Update loopback.js

[jackzelenkin]

Description
On a Mac, loopbackAnswer contains \r\n characters instead of proper line breaks. Because of that initial regex /a=crypto:[1-9]+ .*/g matches everything starting from a=crypto:1 and all the way to the end of loopbackAnswer, and when replaced for an empty string it corrupts the json.

Solution
As a solution, I propose to first search-and-replace "mac-specific" crypto patterns (crypto all the way to first \r\n sequence) and only after that search-and-replace original patterns (crypto all the way to the end of the line).

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here with @googlebot I signed it! and we'll verify it.

---

What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

ℹ️ Googlers: Go here for more info.

[jackzelenkin]

@googlebot I signed it!

[googlebot]

CLAs look good, thanks!

ℹ️ Googlers: Go here for more info.

[alvestrand]

Wrong fix, I think.
\r\n is the specified line termination character in SDP, \n is exceptionally (but universally) accepted.
@fippo should look at this - either the pattern leaves a blank line (just the \r\n or \n), or it eats the \n when there's no \r and doesn't eat it when it's present.
I think you need extra regex modifiers to get substitutes to work past linebreaks (of any type).

[fippo]

The code takes loopbackAnswer as wssMessage.msg which is the serialized JSON which escapes all the SDP crlfs as \r\n. That is a bit silly and unexpected...
And yes, the pattern leaves blank lines, thank you! #667 should fix both

[jackzelenkin]

Thanks Philipp!