Fix asserts in StackFrameIterator which were effectively disabled

runtime/vm/os.h

 // Copyright (c) 2011, 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.
 
 #ifndef RUNTIME_VM_OS_H_
 #define RUNTIME_VM_OS_H_
 
 #include "vm/globals.h"
 
 // Forward declarations.
@@ skipping 58 matching lines @@
   static intptr_t ActivationFrameAlignment();
 
   // This constant is guaranteed to be greater or equal to the
   // preferred code alignment on all platforms.
   static const int kMaxPreferredCodeAlignment = 32;
 
   // Returns the preferred code alignment or zero if
   // the platform doesn't care. Guaranteed to be a power of two.
   static intptr_t PreferredCodeAlignment();
 
-  // Returns true if StackFrameIterator can be used from an isolate that isn't
-  // the calling thread's current isolate.
-  static bool AllowStackFrameIteratorFromAnotherThread();
-
   // Returns number of available processor cores.
   static int NumberOfAvailableProcessors();
 
   // Returns the maximium resident set size of this process.
   static uintptr_t MaxRSS();
 
   // Sleep the currently executing thread for millis ms.
   static void Sleep(int64_t millis);
 
   // Sleep the currently executing thread for micros microseconds.
@@ skipping 58 matching lines @@
   static void Shutdown();
 
   static void Abort();
 
   static void Exit(int code);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_OS_H_