Support SurfaceView synchronization.

Add API for fetching the next frame number to be produced by
a given buffer producer. Add an API to SurfaceComposer to 
defer execution of the current transaction until a given frame number. 
Together these may be used to synchronize app drawing and surface 
control updates.

Change-Id: I8e0f4993332ac0199c768c88581a453fefbaff1d
diff --git a/include/gui/SurfaceComposerClient.h b/include/gui/SurfaceComposerClient.h
index 37d953e..aa48718 100644
--- a/include/gui/SurfaceComposerClient.h
+++ b/include/gui/SurfaceComposerClient.h
@@ -134,6 +134,8 @@
     status_t    setSize(const sp<IBinder>& id, uint32_t w, uint32_t h);
     status_t    setCrop(const sp<IBinder>& id, const Rect& crop);
     status_t    setLayerStack(const sp<IBinder>& id, uint32_t layerStack);
+    status_t    deferTransactionUntil(const sp<IBinder>& id,
+            const sp<IBinder>& handle, uint64_t frameNumber);
     status_t    destroySurface(const sp<IBinder>& id);
 
     status_t clearLayerFrameStats(const sp<IBinder>& token) const;