dillon1000/react

Fix rootElementsByReactRootID bookkeeping in ReactMount.js.

It's not always possible to update `rootElementsByReactRootID` when the
contents of the container are re-rendered; for instance, when we call
`dangerouslyReplaceNodeWithMarkup` or `dangerouslySetInnerHTML`. Since
this bookkeeping is just trying to warn about potentially problematic
manipulations of the root element, and we can be relatively sure that a
new element with the same ID is logically the same element, this diff
avoids warning in such cases.