--- old/src/share/vm/jfr/recorder/checkpoint/types/jfrType.cpp	2019-03-11 12:58:26.955344184 +0800
+++ new/src/share/vm/jfr/recorder/checkpoint/types/jfrType.cpp	2019-03-11 12:58:26.806348501 +0800
@@ -188,13 +188,12 @@
 }
 
 void G1HeapRegionTypeConstant::serialize(JfrCheckpointWriter& writer) {
-  // XXX TODO?
-//  static const u4 nof_entries = G1HeapRegionTraceType::G1HeapRegionTypeEndSentinel;
-//  writer.write_count(nof_entries);
-//  for (u4 i = 0; i < nof_entries; ++i) {
-//    writer.write_key(i);
-//    writer.write(G1HeapRegionTraceType::to_string((G1HeapRegionTraceType::Type)i));
-//  }
+  static const u4 nof_entries = G1HeapRegionTraceType::G1HeapRegionTypeEndSentinel;
+  writer.write_count(nof_entries);
+  for (u4 i = 0; i < nof_entries; ++i) {
+    writer.write_key(i);
+    writer.write(G1HeapRegionTraceType::to_string((G1HeapRegionTraceType::Type)i));
+  }
 }
 
 void GCThresholdUpdaterConstant::serialize(JfrCheckpointWriter& writer) {