BQ: Add and expose a unique id

Bug 29422927

Change-Id: I80eab94f073ebc378302f00fa86a740c3643657e
diff --git a/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp b/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp
index bc8dfbb..c0baa49 100644
--- a/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp
+++ b/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp
@@ -612,6 +612,11 @@
     return INVALID_OPERATION;
 }
 
+status_t VirtualDisplaySurface::getUniqueId(uint64_t* /*outId*/) const {
+    ALOGE("getUniqueId not supported on VirtualDisplaySurface");
+    return INVALID_OPERATION;
+}
+
 void VirtualDisplaySurface::updateQueueBufferOutput(
         const QueueBufferOutput& qbo) {
     uint32_t w, h, transformHint, numPendingBuffers;