Make the injection of ReactPerf work

The injection was only evaluated when ReactCompositeComponent was first loaded.
This made it impossible to inject a custom measure and the injection pointless.
Add `displayName` for DOM Components
Set _renderedComponent before it's fully mounted

For debugging so that we can inspect the currently rendering tree. I think this
should be safe and makes sense since it tried to mount.
Make transferPropsTo() message easier to debug

Summary:
Made the transferPropsTo() error introduced in
325322898cc413454feede0201b61da1abe1e67e easier to use to debug.