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/IGraphicBufferProducer.h b/include/gui/IGraphicBufferProducer.h
index b8cba2f..4586839 100644
--- a/include/gui/IGraphicBufferProducer.h
+++ b/include/gui/IGraphicBufferProducer.h
@@ -508,6 +508,9 @@
 
     // Returns the name of the connected consumer.
     virtual String8 getConsumerName() const = 0;
+
+    // Returns the number of the next frame which will be dequeued.
+    virtual uint64_t getNextFrameNumber() const = 0;
 };
 
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