One of the ReactMultiChildText tests renders 2145 roots (and even more components) and unmounts none of them. Now we don't loop through them all a bunch of times so the test takes 20 seconds instead of 60.
We should clean up instantiateReactComponent somehow so that the onSetDisplayName call isn't produced for the TopLevelWrapper, which should allow us to just store an array of unmountedIDs instead of a hash map so we at least don't have double maps. This change mirrors the old logic though.
Reviewers: @gaearon, @sebmarkbage
Being able to get the source for your parent components seems useful, and ReactComponentTreeDevtool is best poised to be able to do that.
I'm also not sure it makes sense to have separate DOM-specific `onMountDOMComponent` and `onUpdateDOMComponent` events, so I removed them for now. Even if we want them, their timing seemed sort of arbitrary.
I also made it so DOM devtools can listen to non-DOM events too. Willing to change that if people think it's ugly though.
`ReactDebugTool` used to only call `purgeUnmountedComponents()` while profiling, so information about unmounted instances kept accumulating when not profiling.
Additionally, unmounting in React Native and rendering to string did not correctly clean up the devtool.
Finally, the tests tested the wrong behavior and relied on explicit `purgeUnmountedComponent()` calls.
To fix this, we:
* Test specifically that unmounting is enough to clean up the tree devtool.
* Add missing `onBeginFlush` and `onEndFlush` calls to server and native rendering so `ReactDebugTool` knows when to copy the tree.
Fixes#6750
Ben Alpert
Dan Abramov