Add fb-messenger to safe url pattern.
Add fb-messenger to safe url pattern.

RELNOTES[NEW]: Added function goog.html.SafeUrl.fromFacebookMessengerUrl to generate 'fb-messenger://share' urls in a fashion similar to 'tel:' and 'sms:' urls.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=212656945

google/closure-library,teppeis/closure-library,lucidsoftware/closure-library,google/closure-library,teppeis/closure-library,lucidsoftware/closure-library,google/closure-library,lucidsoftware/closure-library,teppeis/closure-library,teppeis/closure-library,lucidsoftware/closure-library,google/closure-library,google/closure-library