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

src/platform-posix.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 11 matching lines @@
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Platform specific code for POSIX goes here. This is not a platform on its
 // own but contains the parts which are the same across POSIX platforms Linux,
 // Mac OS, FreeBSD and OpenBSD.
 
-#include "platform-posix.h"
-
 #include <dlfcn.h>
 #include <pthread.h>
 #if defined(__DragonFly__) || defined(__FreeBSD__) || defined(__OpenBSD__)
 #include <pthread_np.h>  // for pthread_set_name_np
 #endif
 #include <sched.h>  // for sched_yield
 #include <unistd.h>
 #include <errno.h>
 #include <time.h>
 
@@ skipping 687 matching lines @@
 
 void Thread::SetThreadLocal(LocalStorageKey key, void* value) {
   pthread_key_t pthread_key = LocalKeyToPthreadKey(key);
   int result = pthread_setspecific(pthread_key, value);
   ASSERT_EQ(0, result);
   USE(result);
 }
 
 
 } }  // namespace v8::internal