Restore "Add current rss and embedder name to Observatory"

runtime/vm/os_macos.cc

Index: runtime/vm/os_macos.cc
diff --git a/runtime/vm/os_macos.cc b/runtime/vm/os_macos.cc
index 25e36162a16f0fee22c9757868d8d5d26345791c..f8ea9ab35e992f85ca7e9907cab1739623a95fbd 100644
--- a/runtime/vm/os_macos.cc
+++ b/runtime/vm/os_macos.cc
@@ -200,14 +200,6 @@ int OS::NumberOfAvailableProcessors() {
   return sysconf(_SC_NPROCESSORS_ONLN);
 }
 
-uintptr_t OS::MaxRSS() {
-  struct rusage usage;
-  usage.ru_maxrss = 0;
-  int r = getrusage(RUSAGE_SELF, &usage);
-  ASSERT(r == 0);
-  return usage.ru_maxrss;
-}
-
 void OS::Sleep(int64_t millis) {
   int64_t micros = millis * kMicrosecondsPerMillisecond;
   SleepMicros(micros);