protos: Add a comment about zero-valued interning IDs
Bug: 123864183
Change-Id: I37c421736a803471475eab5cdf0da61e499bc2dc
diff --git a/protos/perfetto/trace/perfetto_trace.proto b/protos/perfetto/trace/perfetto_trace.proto
index fc3c02f..2f333e2 100644
--- a/protos/perfetto/trace/perfetto_trace.proto
+++ b/protos/perfetto/trace/perfetto_trace.proto
@@ -2338,7 +2338,7 @@
// The writer will emit new entries when it encounters new internable values
// that aren't yet in the index. Data in current and subsequent TracePackets can
// then refer to the entry by its position (interning ID, abbreviated "iid") in
-// its index.
+// its index. An interning ID with value 0 is considered invalid (not set).
//
// Because of the incremental build-up, the interning index will miss data when
// TracePackets are lost, e.g. because a chunk was overridden in the central