Bug 1092978 - Part1: [Silk] Implemeint RefreshTimerVsyncDispatcher.
Bug 1092978 - Part2: [Silk] Add RefreshTimerDispatcher into VsyncSource::Display.

1) Create RefreshTimerDispatcher in VsyncSource::Display.
2) Use mutex for all VsyncSource::Display's member access.
Bug 1092978 - Part3: [Silk] PVsync protocol for vsync event passing.
Bug 1092978 - Part4: [Silk] Handle PVsync protocol clone message for nuwa.
Bug 1092978 - Part5: [Silk] Extract timer rate function from RefreshDriverTimer into SimpleTimerBasedRefreshTimer.
Bug 1092978 - Part6: [Silk] Vsync aligned refresh timer

1) Handle PVsync async creation.
2) Create vsync-base refresh timer.
WIP, fix b2g silk vsync source impl