Add "is "accessor to referenceCounted in ShadowWakeLock

- Also make getLatestWakeLock static since you don't need an instance.
- Add the ShadowWakeLock to the shadowOf method list.
Add test for ShadowWakeLock
Merge pull request #742 from SuperJugy/ShadowWakeLock

Add "is "accessor to referenceCounted in ShadowWakeLock