Add --print-benchmarking-metrics to the VM for Golem.

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index 8304532470999c81ea515843ad6496c8348db0f3..11dce365923c0389d13287f21323aec3ea493f26 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -1187,6 +1187,16 @@ bool Isolate::MakeRunnable() {
     Service::HandleEvent(&runnableEvent);
   }
 #endif  // !PRODUCT
+  GetRunnableLatencyMetric()->set_value(UptimeMicros());
+  if (FLAG_print_benchmarking_metrics) {
+    {
+      StartIsolateScope scope(this);
+      heap()->CollectAllGarbage();
+    }
+    int64_t heap_size = (heap()->UsedInWords(Heap::kNew) * kWordSize) +
+                        (heap()->UsedInWords(Heap::kOld) * kWordSize);
+    GetRunnableHeapSizeMetric()->set_value(heap_size);
+  }
   return true;
 }
 
@@ -1682,13 +1692,12 @@ void Isolate::LowLevelShutdown() {
         "\tisolate:    %s\n",
         name());
   }
-  if (FLAG_print_metrics) {
+  if (FLAG_print_metrics || FLAG_print_benchmarking_metrics) {
     LogBlock lb;
     OS::PrintErr("Printing metrics for %s\n", name());
 #define ISOLATE_METRIC_PRINT(type, variable, name, unit)                       \
   OS::PrintErr("%s\n", metric_##variable##_.ToString());
-
-    ISOLATE_METRIC_LIST(ISOLATE_METRIC_PRINT);
+    ISOLATE_METRIC_LIST(ISOLATE_METRIC_PRINT)
 #undef ISOLATE_METRIC_PRINT
     OS::PrintErr("\n");
   }