Bug 1092978 - Part4: [Silk] vsync-aligned refresh driver

1. add "gfx.vsync.refresh-driver" pref to turn on/off vsync-aligned refresh driver
2. observe vsync event to tick refresh driver.
3. refactor nsRefreshDriver::Tick(). We have Tick() and Tick(TimeStamp) now.
add systrace tracer
add systrace tag for RD and vsync event
debug DidComposite() ipc message
debug CompositorParent composing time