Do not spam error log for malformed traces

We already log a stat, there's not much value added by repeating the
invalid id msg

Change-Id: I44436957ce83111ac6beef0684ab0afb2cc1c4e5
diff --git a/src/trace_processor/importers/proto/heap_graph_tracker.cc b/src/trace_processor/importers/proto/heap_graph_tracker.cc
index e9b400d..f4e4f70 100644
--- a/src/trace_processor/importers/proto/heap_graph_tracker.cc
+++ b/src/trace_processor/importers/proto/heap_graph_tracker.cc
@@ -580,7 +580,7 @@
                   current_type->field_name_ids[field_offset_in_cls++];
               auto it = sequence_state.interned_fields.find(field_id);
               if (it == sequence_state.interned_fields.end()) {
-                PERFETTO_ELOG("Invalid field id.");
+                PERFETTO_DLOG("Invalid field id.");
                 context_->storage->IncrementIndexedStats(
                     stats::heap_graph_malformed_packet,
                     static_cast<int>(sequence_state.current_upid));