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

src/platform-cygwin.cc

Index: src/platform-cygwin.cc
diff --git a/src/platform-cygwin.cc b/src/platform-cygwin.cc
index 5903438932b61ad6eea29c7cac5441bca78c632a..991b402882c6b57b4e7810651414eea0678b2d0d 100644
--- a/src/platform-cygwin.cc
+++ b/src/platform-cygwin.cc
@@ -205,6 +205,18 @@ void OS::SignalCodeMovingGC() {
 }
 
 
+uintptr_t OS::TotalPhysicalMemory() {
+  MEMORYSTATUS memory_info;
+  memory_info.dwLength = sizeof(memory_info);
+  if (!GlobalMemoryStatus(&memory_info)) {
+    UNREACHABLE();
+    return 0;
+  }
+
+  return static_cast<uintptr_t>(memory_info.dwTotalPhys);
+}
+
+
 // The VirtualMemory implementation is taken from platform-win32.cc.
 // The mmap-based virtual memory implementation as it is used on most posix
 // platforms does not work well because Cygwin does not support MAP_FIXED.