VM: Teach GetAndValidateIsolateStackBounds(...) to fallback to OS thread stack bounds.

runtime/vm/os_thread.h

 // 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.
 
 #ifndef RUNTIME_VM_OS_THREAD_H_
 #define RUNTIME_VM_OS_THREAD_H_
 
 #include "platform/globals.h"
 #include "vm/allocation.h"
 #include "vm/globals.h"
@@ skipping 90 matching lines @@
     uword stack_upper = stack_base_;
     if (stack_upper == 0) {
       return false;
     }
     uword stack_lower = stack_upper - GetSpecifiedStackSize();
     *lower = stack_lower;
     *upper = stack_upper;
     return true;
   }
 
+  static bool GetCurrentStackBounds(uword* lower, uword* upper);
+
   // Used to temporarily disable or enable thread interrupts.
   void DisableThreadInterrupts();
   void EnableThreadInterrupts();
   bool ThreadInterruptsEnabled();
 
   // The currently executing thread, or NULL if not yet initialized.
   static OSThread* Current() {
     BaseThread* thread = GetCurrentTLS();
     OSThread* os_thread = NULL;
     if (thread != NULL) {
@@ skipping 221 matching lines @@
   friend class SafepointMonitorLocker;
   friend void Dart_TestMonitor();
   DISALLOW_COPY_AND_ASSIGN(Monitor);
 };
 
 
 }  // namespace dart
 
 
 #endif  // RUNTIME_VM_OS_THREAD_H_