Rollback trunk to 3.21.15.

src/platform-cygwin.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 187 matching lines @@
   free(lib_name);
   fclose(fp);
 }
 
 
 void OS::SignalCodeMovingGC() {
   // Nothing to do on Cygwin.
 }
 
 
+int OS::StackWalk(Vector<OS::StackFrame> frames) {
+  // Not supported on Cygwin.
+  return 0;
+}
+
+
 // 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.
 // This causes VirtualMemory::Commit to not always commit the memory region
 // specified.
 
 static void* GetRandomAddr() {
   Isolate* isolate = Isolate::UncheckedCurrent();
   // Note that the current isolate isn't set up in a call path via
   // CpuFeatures::Probe. We don't care about randomization in this case because
@@ skipping 136 matching lines @@
   return VirtualFree(base, 0, MEM_RELEASE) != 0;
 }
 
 
 bool VirtualMemory::HasLazyCommits() {
   // TODO(alph): implement for the platform.
   return false;
 }
 
 } }  // namespace v8::internal