Restore "Add current rss and embedder name to Observatory"

runtime/vm/metrics.h

Index: runtime/vm/metrics.h
diff --git a/runtime/vm/metrics.h b/runtime/vm/metrics.h
index 87467ce5ee5f0192e80653dcdcb4bf334bc3ff0d..530cc4dd7d05515c8c07cf9709343d74fd47b163 100644
--- a/runtime/vm/metrics.h
+++ b/runtime/vm/metrics.h
@@ -31,6 +31,7 @@ class JSONStream;
 
 #define VM_METRIC_LIST(V)                                                      \
   V(MetricIsolateCount, IsolateCount, "vm.isolate.count", kCounter)            \
+  V(MetricCurrentRSS, CurrentRSS, "vm.memory.current", kByte)                  \
   V(MetricPeakRSS, PeakRSS, "vm.memory.max", kByte)
 
 class Metric {
@@ -162,6 +163,11 @@ class MetricIsolateCount : public Metric {
   virtual int64_t Value() const;
 };
 
+class MetricCurrentRSS : public Metric {
+ protected:
+  virtual int64_t Value() const;
+};
+
 class MetricPeakRSS : public Metric {
  protected:
   virtual int64_t Value() const;