Fix asserts in StackFrameIterator which were effectively disabled

runtime/vm/os_linux.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_LINUX)
 
 #include "vm/os.h"
 
 #include <errno.h>         // NOLINT
@@ skipping 215 matching lines @@
   // TODO(5411554): Allow overriding default code alignment for
   // testing purposes.
   // Flags::DebugIsInt("codealign", &alignment);
   ASSERT(Utils::IsPowerOfTwo(alignment));
   ASSERT(alignment >= kMinimumAlignment);
   ASSERT(alignment <= OS::kMaxPreferredCodeAlignment);
   return alignment;
 }
 
 
-bool OS::AllowStackFrameIteratorFromAnotherThread() {
-  return false;
-}
-
-
 int OS::NumberOfAvailableProcessors() {
   return sysconf(_SC_NPROCESSORS_ONLN);
 }
 
 
 uintptr_t OS::MaxRSS() {
   struct rusage usage;
   usage.ru_maxrss = 0;
   int r = getrusage(RUSAGE_SELF, &usage);
   ASSERT(r == 0);
@@ skipping 171 matching lines @@
 }
 
 
 void OS::Exit(int code) {
   exit(code);
 }
 
 }  // namespace dart
 
 #endif  // defined(HOST_OS_LINUX)