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 7708047f003a3f7acb3a28d864f45718a26aeba5..ea0666b0790119dfdfa3a78fcba111b163bdc552 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -1182,6 +1182,20 @@ bool Isolate::MakeRunnable() {
     Service::HandleEvent(&runnableEvent);
   }
 #endif  // !PRODUCT
+  if (FLAG_print_benchmarking_metrics) {
+    // is_service_isolate not set yet.
+    if (!ServiceIsolate::NameEquals(name())) {
+      int64_t uptime = OS::GetCurrentTimeMicros() - start_time();

[sortie, 2016/12/14 19:09:52]

This interval seems to be measure in wall seconds (subject to time changes, leap
second smearing, etc.) rather than monotonic time.

[rmacnak, 2016/12/16 19:10:22]

Fixed this in another CL.

+      OS::Print("MakeRunnable(Latency): %" Pd64 " us.\n", uptime);

[Cutch, 2016/12/14 18:34:36]

Please use the metric support in metrics.h instead of rolling your own.

+      {
+        StartIsolateScope scope(this);
+        heap()->CollectAllGarbage();
+      }
+      int64_t heap_size = (heap()->UsedInWords(Heap::kNew) * kWordSize) +
+                          (heap()->UsedInWords(Heap::kOld) * kWordSize);
+      OS::Print("MakeRunnable(HeapSize): %" Pd64 " B.\n", heap_size);
+    }
+  }
   return true;
 }