dillon1000/react

Remove ReactID.primeTree in favor of priming in ReactID.getID.

Although it would have been nice to prime the entire tree and achieve a
cache hit rate of 100%, that cost would have to be paid up front, during
page rendering.

This patch avoids priming up front in favor of making the most of the work
done by `ReactMount.findReactRenderedDOMNodeSlow`, which calls
`ReactID.getID` while traversing the rendered DOM. The insight is this: if
`getID` simply primes the cache whenever it finds a new ID, then
`findReactRenderedDOMNodeSlow` will end up priming quite a few more nodes
that are actually involved in `ReactID.getNode` lookups, and we won't need
`primeTree` at all.