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

src/platform-macos.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 184 matching lines @@
     LOG(isolate,
         SharedLibraryEvent(_dyld_get_image_name(i), start, start + size));
   }
 }
 
 
 void OS::SignalCodeMovingGC() {
 }
 
 
+uintptr_t OS::TotalPhysicalMemory() {
+  int mib[2];
+  mib[0] = CTL_HW;
+  mib[1] = HW_MEMSIZE;
+  int64_t size = 0;
+  size_t len = sizeof(size);
+  if (sysctl(mib, 2, &size, &len, NULL, 0) == 0)
+    return static_cast<uintptr_t> size;
+  UNREACHABLE();
+  return 0;
+}
+
+
 const char* OS::LocalTimezone(double time) {
   if (std::isnan(time)) return "";
   time_t tv = static_cast<time_t>(floor(time/msPerSecond));
   struct tm* t = localtime(&tv);
   if (NULL == t) return "";
   return t->tm_zone;
 }
 
 
 double OS::LocalTimeOffset() {
@@ skipping 131 matching lines @@
 bool VirtualMemory::ReleaseRegion(void* address, size_t size) {
   return munmap(address, size) == 0;
 }
 
 
 bool VirtualMemory::HasLazyCommits() {
   return false;
 }
 
 } }  // namespace v8::internal