BQ: Add and expose a unique id

Bug 29422927

Change-Id: I80eab94f073ebc378302f00fa86a740c3643657e
diff --git a/libs/gui/BufferQueueProducer.cpp b/libs/gui/BufferQueueProducer.cpp
index be3b6c3..234a863 100644
--- a/libs/gui/BufferQueueProducer.cpp
+++ b/libs/gui/BufferQueueProducer.cpp
@@ -1422,4 +1422,11 @@
     disconnect(api);
 }
 
+status_t BufferQueueProducer::getUniqueId(uint64_t* outId) const {
+    BQ_LOGV("getUniqueId");
+
+    *outId = mCore->mUniqueId;
+    return NO_ERROR;
+}
+
 } // namespace android