Move DumpBacktrace() to checks.cc and cleanup both the code and the necessary platform checks.

src/platform.h

 // 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 238 matching lines @@
 
   // Sleep for a number of milliseconds.
   static void Sleep(const int milliseconds);
 
   // Abort the current process.
   static void Abort();
 
   // Debug break.
   static void DebugBreak();
 
-  // Dump C++ current stack trace (only functional on Linux).
-  static void DumpBacktrace();
-
   // Walk the stack.
   static const int kStackWalkError = -1;
   static const int kStackWalkMaxNameLen = 256;
   static const int kStackWalkMaxTextLen = 256;
   struct StackFrame {
     void* address;
     char text[kStackWalkMaxTextLen];
   };
 
   class MemoryMappedFile {
@@ skipping 320 matching lines @@
   char name_[kMaxThreadNameLength];
   int stack_size_;
   Semaphore* start_semaphore_;
 
   DISALLOW_COPY_AND_ASSIGN(Thread);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_H_