VM: Remove too strict assertion in rethrow.

runtime/vm/exceptions.cc

Index: runtime/vm/exceptions.cc
diff --git a/runtime/vm/exceptions.cc b/runtime/vm/exceptions.cc
index 4b73efd02026d37a0fefc1ab894238631bf9667d..8fde8b43f906e03a6fcf074e063d3d707f6a2e51 100644
--- a/runtime/vm/exceptions.cc
+++ b/runtime/vm/exceptions.cc
@@ -415,8 +415,6 @@ static void ThrowExceptionHelper(Thread* thread,
       // reverse is not necessarily true (e.g. Dart_PropagateError can cause
       // a rethrow being called without an existing stacktrace.)
       ASSERT(is_rethrow);
-      ASSERT(stacktrace_field.IsNull() ||
-             (exception.GetField(stacktrace_field) != Object::null()));
       stacktrace = existing_stacktrace.raw();

[kustermann, 2016/11/17 11:07:48]

This branch doesn't need [stacktrace_field] anymore. Maybe only do the
Field::Handle(zone, LookupStacktraceField(exception) in the else-case?

[Florian Schneider, 2016/11/17 18:59:07]

Done.

     } else if (!stacktrace_field.IsNull() || handler_needs_stacktrace) {
       // Collect the stacktrace if needed.