Correctly count heapprofd_missing_packet.

Change-Id: I69fdb31eb6015f104acf8a54bd1df6e3963b1bb1

src/trace_processor/heap_profile_tracker.cc

diff --git a/src/trace_processor/heap_profile_tracker.cc b/src/trace_processor/heap_profile_tracker.cc
index 1a786fc..67883fc 100644
--- a/src/trace_processor/heap_profile_tracker.cc
+++ b/src/trace_processor/heap_profile_tracker.cc
@@ -227,11 +227,27 @@
 void HeapProfileTracker::SetProfilePacketIndex(uint32_t seq_id,
                                                uint64_t index) {
   SequenceState& sequence_state = sequence_state_[seq_id];
-  if (sequence_state.last_profile_packet_index != 0 &&
-      sequence_state.last_profile_packet_index + 1 != index) {
+  bool dropped_packet = false;
+  // heapprofd starts counting at index = 0.
+  if (!sequence_state.prev_index && index != 0) {
+    dropped_packet = true;
+  }
+
+  if (sequence_state.prev_index && *sequence_state.prev_index + 1 != index) {
+    dropped_packet = true;
+  }
+
+  if (dropped_packet) {
+    if (sequence_state.prev_index) {
+      PERFETTO_ELOG("Missing packets between %" PRIu64 " and %" PRIu64,
+                    *sequence_state.prev_index, index);
+    } else {
+      PERFETTO_ELOG("Invalid first packet index %" PRIu64 " (!= 0)", index);
+    }
+
     context_->storage->IncrementStats(stats::heapprofd_missing_packet);
   }
-  sequence_state.last_profile_packet_index = index;
+  sequence_state.prev_index = index;
 }
 
 void HeapProfileTracker::AddAllocation(

src/trace_processor/heap_profile_tracker.h

diff --git a/src/trace_processor/heap_profile_tracker.h b/src/trace_processor/heap_profile_tracker.h
index 12cd2da..fe40a84 100644
--- a/src/trace_processor/heap_profile_tracker.h
+++ b/src/trace_processor/heap_profile_tracker.h
@@ -110,7 +110,7 @@
              tables::HeapProfileAllocationTable::Row>
         free_correction;
 
-    uint64_t last_profile_packet_index = 0;
+    base::Optional<uint64_t> prev_index;
   };
   std::map<uint32_t, SequenceState> sequence_state_;
   TraceProcessorContext* const context_;