Make the use of Unsafe conditional

[eed3si9n]

Ref #3781

This is an attempt to workaround the Unsafe warning on JDK 9+.

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[eed3si9n]

I signed it!

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CLAs look good, thanks!

[xfxyjwf]

@eed3si9n Thanks for the patch, but I don't think we can just disable unsafe like this as we have code paths relying on the use of unsafe. I'm working on integrating our internal Java changes to github right now and we should fix the Java 9 issue after all the changes are integrated.

[xfxyjwf]

I'm closing this PR for now.

[eed3si9n]

@xfxyjwf Could you update the status on #3781 please?
What's the expected schedule for the integration?