Fix asserts in StackFrameIterator which were effectively disabled

runtime/vm/os_win.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(HOST_OS_WINDOWS)
 
 #include "vm/os.h"
 
 #include <malloc.h>   // NOLINT
@@ skipping 198 matching lines @@
     defined(TARGET_ARCH_ARM64) || defined(TARGET_ARCH_DBC)
   return 32;
 #elif defined(TARGET_ARCH_ARM) || defined(TARGET_ARCH_MIPS)
   return 16;
 #else
 #error Unsupported architecture.
 #endif
 }
 
 
-bool OS::AllowStackFrameIteratorFromAnotherThread() {
-  return true;
-}
-
-
 int OS::NumberOfAvailableProcessors() {
   SYSTEM_INFO info;
   GetSystemInfo(&info);
   return info.dwNumberOfProcessors;
 }
 
 
 uintptr_t OS::MaxRSS() {
   PROCESS_MEMORY_COUNTERS pmc;
   GetProcessMemoryInfo(GetCurrentProcess(), &pmc, sizeof(pmc));
@@ skipping 216 matching lines @@
   // TODO(zra): Remove once VM shuts down cleanly.
   private_flag_windows_run_tls_destructors = false;
   // On Windows we use ExitProcess so that threads can't clobber the exit_code.
   // See: https://code.google.com/p/nativeclient/issues/detail?id=2870
   ::ExitProcess(code);
 }
 
 }  // namespace dart
 
 #endif  // defined(HOST_OS_WINDOWS)