Revert Dart_PropagateError until I can track down the problems in

runtime/vm/longjump.cc

Index: runtime/vm/longjump.cc
===================================================================
--- runtime/vm/longjump.cc	(revision 3821)
+++ runtime/vm/longjump.cc	(working copy)
@@ -20,20 +20,9 @@
 }
 
 
-bool LongJump::IsSafeToJump() {
-  // We do not want to jump past Dart frames.  Note that this code
-  // assumes the stack grows from high to low.
-  Isolate* isolate = Isolate::Current();
-  uword jumpbuf_addr = reinterpret_cast<uword>(this);
-  return (isolate->top_exit_frame_info() == 0 ||
-          jumpbuf_addr < isolate->top_exit_frame_info());
-}
-
-
 void LongJump::Jump(int value, const Error& error) {
   // A zero is the default return value from setting up a LongJump using Set.
   ASSERT(value != 0);
-  ASSERT(IsSafeToJump());
 
   Isolate* isolate = Isolate::Current();