Observatory: Report peak process memory usage.

runtime/vm/os_win.cc

Index: runtime/vm/os_win.cc
diff --git a/runtime/vm/os_win.cc b/runtime/vm/os_win.cc
index 7236a9164959810a6bf96c85f5786aed3f8adc1a..1bf89bd4a278eb598da919e658f356e2190ec5bd 100644
--- a/runtime/vm/os_win.cc
+++ b/runtime/vm/os_win.cc
@@ -9,6 +9,7 @@
 
 #include <malloc.h>  // NOLINT
 #include <process.h>  // NOLINT
+#include <psapi.h>  // NOLINT
 #include <time.h>  // NOLINT
 
 #include "platform/utils.h"
@@ -235,6 +236,13 @@ int OS::NumberOfAvailableProcessors() {
 }
 
 
+uinptr_t OS::MaxRSS() {
+  PROCESS_MEMORY_COUNTERS pmc;
+  GetProcessMemoryInfo(GetCurrentProcess(), &pmc, sizeof(pmc));
+  return pmc.PeakWorkingSetSize;
+}
+
+
 void OS::Sleep(int64_t millis) {
   ::Sleep(millis);
 }