RFR: 6542: Improve calls to render in the flame view

[Miroslav Wengner]

On Fri, 5 Jun 2020 14:35:20 GMT, Marcus Hirt <hirt at openjdk.org> wrote:

>> stable flameview generation
>
> Sadly I can still make it go out of whack with these changes:
> ![image](https://user-images.githubusercontent.com/16906077/83888656-71fc4c80-a74a-11ea-9c03-1cfa0c28569e.png)

I've add a fix.

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PR: https://git.openjdk.java.net/jmc/pull/78