Perfetto: Fixed crash due to missing referenced frames on JSON output

R=ssid@chromium.org

Bug: 983895
Change-Id: I619c2a789855da1d387a9e9504b186ce4fb23755
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1701611
Auto-Submit: oysteine <oysteine@chromium.org>
Reviewed-by: ssid <ssid@chromium.org>
Commit-Queue: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#677427}

services/tracing/perfetto/track_event_json_exporter.cc

@@ -539,7 +539,10 @@ void TrackEventJSONExporter::HandleStreamingProfilePacket(
   std::string result;
   for (const auto& frame_id : callstack->second) {
     auto frame = current_state_->interned_frames_.find(frame_id);
-    DCHECK(frame != current_state_->interned_frames_.end());
+    if (frame == current_state_->interned_frames_.end()) {
+      base::StringAppendF(&result, "MISSING FRAME REFERENCE - ???\n");
+      continue;
+    }
 
     std::string frame_name;
     std::string module_name;