Introduce global contexts to represent lexical global scope(s).

src/objects-debug.cc

 // 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 364 matching lines @@
               BitCast<uint64_t>(canonical_not_the_hole_nan_as_double())) ||
              ((BitCast<uint64_t>(value) & Double::kSignMask) != 0));
     }
   }
 }
 
 
 void JSModule::JSModuleVerify() {
   VerifyObjectField(kContextOffset);
   VerifyObjectField(kScopeInfoOffset);
-  CHECK(context()->IsUndefined() || context()->IsModuleContext());
+  CHECK(context()->IsUndefined() ||
+        Context::cast(context())->IsModuleContext());
 }
 
 
 void JSValue::JSValueVerify() {
   Object* v = value();
   if (v->IsHeapObject()) {
     VerifyHeapPointer(v);
   }
 }
 
@@ skipping 618 matching lines @@
   FixedArray* proto_transitions = GetPrototypeTransitions();
   MemsetPointer(proto_transitions->data_start(),
                 GetHeap()->the_hole_value(),
                 proto_transitions->length());
 }
 
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal