Add dvrBufferGlobalLayoutVersion which returns the version number for
the global buffers.

Bug: 62228826
Test: dvrBufferGlobalLayoutVersion == kSharedBufferLayoutVersion
Change-Id: I08eaca128ea5c84739924ab839651088e10c65bc
diff --git a/libs/vr/libdvr/dvr_buffer.cpp b/libs/vr/libdvr/dvr_buffer.cpp
index 82469b8..4d9b215 100644
--- a/libs/vr/libdvr/dvr_buffer.cpp
+++ b/libs/vr/libdvr/dvr_buffer.cpp
@@ -1,6 +1,7 @@
 #include "include/dvr/dvr_buffer.h"
 
 #include <android/hardware_buffer.h>
+#include <dvr/dvr_shared_buffers.h>
 #include <private/dvr/buffer_hub_client.h>
 #include <ui/GraphicBuffer.h>
 
@@ -176,6 +177,11 @@
                                   hardware_buffer);
 }
 
+// Retrieve the shared buffer layout version defined in dvr_shared_buffers.h.
+int dvrBufferGlobalLayoutVersionGet() {
+  return android::dvr::kSharedBufferLayoutVersion;
+}
+
 const struct native_handle* dvrWriteBufferGetNativeHandle(
     DvrWriteBuffer* write_buffer) {
   if (!write_buffer || !write_buffer->write_buffer)