Assert that context creation doesn't throw

src/isolate.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/isolate.h"
 
 #include <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
@@ skipping 1675 matching lines @@
   // external handler which is on top of the top-most JS_ENTRY handler.
   //
   // Note, that finally clauses would re-throw an exception unless it's aborted
   // by jumps in control flow (like return, break, etc.) and we'll have another
   // chance to set proper v8::TryCatch later.
   return (entry_handler > external_handler);
 }
 
 
 void Isolate::ReportPendingMessages() {
+  DCHECK(AllowExceptions::IsAllowed(this));
+
   Object* exception = pending_exception();
 
   // Try to propagate the exception to an external v8::TryCatch handler. If
   // propagation was unsuccessful, then we will get another chance at reporting
   // the pending message if the exception is re-thrown.
   bool has_been_propagated = PropagatePendingExceptionToExternalTryCatch();
   if (!has_been_propagated) return;
 
   // Clear the pending message object early to avoid endless recursion.
   Object* message_obj = thread_local_top_.pending_message_obj_;
@@ skipping 1945 matching lines @@
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8