Add comment about avoiding VS runtime support to OS::DebugBreak.

src/platform-win32.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 992 matching lines @@
     DebugBreak();
   } else {
     // Make the MSVCRT do a silent abort.
     raise(SIGABRT);
   }
 }
 
 
 void OS::DebugBreak() {
 #ifdef _MSC_VER
+  // To avoid Visual Studio runtime support the following code can be used
+  // instead
+  // __asm { int 3 }
   __debugbreak();
 #else
   ::DebugBreak();
 #endif
 }
 
 
 void OS::DumpBacktrace() {
   // Currently unsupported.
 }
@@ skipping 967 matching lines @@
   limit_mutex = CreateMutex();
 }
 
 
 void OS::TearDown() {
   delete limit_mutex;
 }
 
 
 } }  // namespace v8::internal