Allow StackFrameIterator to be used on a different thread than the isolate whose stack frames are b…

runtime/vm/os.h

Index: runtime/vm/os.h
diff --git a/runtime/vm/os.h b/runtime/vm/os.h
index e2608531b74f21a16d707b80e7e6973f7e60396a..beceeaba1a256110abae7e99fcb299de3363b46d 100644
--- a/runtime/vm/os.h
+++ b/runtime/vm/os.h
@@ -78,6 +78,10 @@ class OS {
   // Returns the stack size limit.
   static uword GetStackSizeLimit();
 
+  // 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();