VM: Prohibit reload when throwing or processing language errors.

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 45ae3ca43e165b355fb4c605139afda2cc25c4e6..8282ed526b96608aaf603eaf34d873308727050b 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -15368,6 +15368,8 @@ RawString* LanguageError::FormatMessage() const {
 
 
 const char* LanguageError::ToErrorCString() const {
+  Thread* thread = Thread::Current();
+  NoReloadScope no_reload_scope(thread->isolate(), thread);
   const String& msg_str = String::Handle(FormatMessage());
   return msg_str.ToCString();
 }
@@ -15425,6 +15427,7 @@ void UnhandledException::set_stacktrace(const Instance& stacktrace) const {
 const char* UnhandledException::ToErrorCString() const {
   Thread* thread = Thread::Current();
   Isolate* isolate = thread->isolate();
+  NoReloadScope no_reload_scope(isolate, thread);
   HANDLESCOPE(thread);
   Object& strtmp = Object::Handle();
   const char* exc_str;