Add methods to enable configuration of ResourceConstraints based on limits derived at runtime.

src/platform-win32.cc

Index: src/platform-win32.cc
diff --git a/src/platform-win32.cc b/src/platform-win32.cc
index 073b21a011aae732b7db5dc15ca3b18c85e3858b..38720513bc8e8a31034d0e1a606f99ff53488ea0 100644
--- a/src/platform-win32.cc
+++ b/src/platform-win32.cc
@@ -1208,6 +1208,18 @@ void OS::SignalCodeMovingGC() {
 }
 
 
+uint64_t OS::TotalPhysicalMemory() {
+  MEMORYSTATUSEX memory_info;
+  memory_info.dwLength = sizeof(memory_info);
+  if (!GlobalMemoryStatusEx(&memory_info)) {
+    UNREACHABLE();
+    return 0;
+  }
+
+  return static_cast<uint64_t>(memory_info.ullTotalPhys);
+}
+
+
 #else  // __MINGW32__
 void OS::LogSharedLibraryAddresses(Isolate* isolate) { }
 void OS::SignalCodeMovingGC() { }