Problem: when adding a view via the add view dialog (found at Window -> Show view -> Other..), the view will not automatically update based on the current page selection if the JFR page is already open. Any users unaware that after adding a view they have to update their current page selection may think that the added page is bugged or not working properly.

Using the Flameview as an example, this can be seen by:
1. Opening a *.jfr file
2. Navigating a to a page to view stack trace information, perhaps the Java Application page
3. Adding the flameview to the screen
4. The flameview will be blank, and not update based on what's currently being selected on the jfr page - until a new selection is made

Note that if the flameview is added first, and then a *.jfr file is opened, the view has no troubles getting the information and displaying it.

Additionally, if the JFR view is closed or a non-JFR related page is opened (e.g., a JMX Console), the flameview continues to show whatever it was displaying previously instead of clearing or displaying some sort of empty state message.

I've attached a couple gifs and a screenshot to illustrate this:
1. jfr-first.gif: the flameview is added while a jfr file is currently opened, and the flameview displays a blank gray screen
2. jfr-second.gif: the flameview is added before the jfr file is opened
3. jfr-closed-flameview.png: the jfr file has been closed, and the flameview retains the information and continues to show it

This issue was raised in a review comment for JMC-6810 [0].

[0] https://github.com/openjdk/jmc/pull/77#pullrequestreview-432753899