Fix for Clusterfuzz issue 343928.

src/contexts.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 208 matching lines @@
 //                ScopeInfo.
 //                For module contexts, points back to the respective JSModule.
 //
 // [ global_object ]  A pointer to the global object. Provided for quick
 //                access to the global object from inside the code (since
 //                we always have a context pointer).
 //
 // In addition, function contexts may have statically allocated context slots
 // to store local variables/functions that are accessed from inner functions
 // (via static context addresses) or through 'eval' (dynamic context lookups).
-// Finally, the native context contains additional slots for fast access to
-// native properties.
+// The native context contains additional slots for fast access to native
+// properties.
+//
+// Finally, with Harmony scoping, the JSFunction representing a top level
+// script will have the GlobalContext rather than a FunctionContext.
 
 class Context: public FixedArray {
  public:
   // Conversions.
   static Context* cast(Object* context) {
     ASSERT(context->IsContext());
     return reinterpret_cast<Context*>(context);
   }
 
   // The default context slot layout; indices are FixedArray slot indices.
@@ skipping 280 matching lines @@
   static bool IsBootstrappingOrGlobalObject(Isolate* isolate, Object* object);
 #endif
 
   STATIC_CHECK(kHeaderSize == Internals::kContextHeaderSize);
   STATIC_CHECK(EMBEDDER_DATA_INDEX == Internals::kContextEmbedderDataIndex);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_CONTEXTS_H_