[firebase_messaging] fix crash when func deleteInstanceID return result in incorrect thread

[wildtigon]

Description

Make result of deleteInstanceID function return in correct UI Thread

Related Issues

flutter/flutter#33265

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Breaking Change

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[wildtigon]

I signed it!

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[kroikie]

@wildtigon thanks for the PR, would you mind using the same approach we have in the cloud_firestore plugin for this?

Also bumping the Version and CHANGELOG would help.

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[wildtigon]

@kroikie: Sorry for late reply, I've changed it to runOnUiThread way. Since deleteInstanceID function in Firebase core doesn't give us callback method. I just want to make small change.

Another question. I've used another PC with broken email information to commit. I can't access this to this to verify alternate email address. Could you help me how can I re-sign CLA in this PR again ?

[collinjackson]

Thanks for the PR!

I added integration tests in #1816.

CLA looks fine.