libgui: Add generation numbers to BufferQueue

This change allows producers to set a generation number on a
BufferQueue. This number will be embedded in any new GraphicBuffers
created in that BufferQueue, and attempts to attach buffers which have
a different generation number will fail.

It also plumbs the setGenerationNumber method through Surface, with the
additional effect that any buffers attached to the Surface after
setting a new generation number will automatically be updated with the
new number (as opposed to failing, as would happen on through IGBP).

Bug: 20923096
Change-Id: I32bf726b035f99c3e5834beaf76afb9f01adcbc2
diff --git a/services/surfaceflinger/MonitoredProducer.cpp b/services/surfaceflinger/MonitoredProducer.cpp
index 9fb555b..6f25bf5 100644
--- a/services/surfaceflinger/MonitoredProducer.cpp
+++ b/services/surfaceflinger/MonitoredProducer.cpp
@@ -114,6 +114,10 @@
     return mProducer->allowAllocation(allow);
 }
 
+status_t MonitoredProducer::setGenerationNumber(uint32_t generationNumber) {
+    return mProducer->setGenerationNumber(generationNumber);
+}
+
 IBinder* MonitoredProducer::onAsBinder() {
     return IInterface::asBinder(mProducer).get();
 }