profiling: Set mapping id in resulting proto.

Change-Id: Ibe3d46cf0b1ecb5bc94f5b121766c95e6330d68e

src/profiling/memory/bookkeeping.cc

diff --git a/src/profiling/memory/bookkeeping.cc b/src/profiling/memory/bookkeeping.cc
index 8f78d25..a52db3c 100644
--- a/src/profiling/memory/bookkeeping.cc
+++ b/src/profiling/memory/bookkeeping.cc
@@ -192,6 +192,7 @@
       WriteString(packet, str);
 
     auto mapping = packet->add_mappings();
+    mapping->set_id(map.id());
     mapping->set_offset(map->offset);
     mapping->set_start(map->start);
     mapping->set_end(map->end);