RFR: 6542: Improve calls to render in the flame view [v20]

[Miroslav Wengner]

On Fri, 9 Oct 2020 20:10:30 GMT, Marcus Hirt <hirt at openjdk.org> wrote:

>> Miroslav Wengner has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   6542: more cleanup
>
> application/org.openjdk.jmc.flightrecorder.flameview/src/main/java/org/openjdk/jmc/flightrecorder/flameview/views/FlameGraphView.java
> line 378:
>> 376:
>> 377: 			TraceNode root = TraceTreeUtils.createRootWithDescription(items, rootFork.getBranchCount());
>> 378: 			if (Thread.currentThread().isAlive()) {
> 
> I don’t get these thread changes. The current thread is executing your code, and is therefore always alive. Also, if
> you want to make these calculations abortable, I’d much prefer an API for it. Maybe an Abortable interface, or perhaps
> even better, providing some sort of a progress interface where progress could be reported to and checked against
> whether it should abort every now and then. We can discuss which alternative makes most sense.

I've reconsidered my thoughts. I wanted to cancel the Task calculations inside the executor thread before it get's
jointed with the main. I've added the Scheduler executor and a bit delay its start, in case of fast scrolling, it's
more transparent. I've also cleared the code.

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