hide VsyncDispatcherHost/Client detail to client user
add VsyncObserver def
get hwc hw vsync period
register refresh driver timer into vsync dispatcher
fix hwc getVsyncPeriod
fix dispatch tick task error
get vsync period from vsync dispatcher
apply bug 820716 to avoid Assertion failure: OOPInitialized()
rebase: hide VsyncDispatcherClient/Host to user
add GetVsyncPeriod ipc call