Add the callback of send operation.

[NathanLi]

Add feature: Callback of send data.

[ghost]

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[NathanLi]

I signed in CLA. Thank you.

[ghost]

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[nlutsenko]

This looks like a nice idea, will review soon and provide some feedback on naming and polish so we can get this merged in!

[NathanLi]

@nlutsenko Thank you for taking the time to review my code. I have changed you mentioned, please review again.

[NathanLi]

Yes, you are right. Use dataRange as a key is correct.

[NathanLi]

@nlutsenko Can you review the code?