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

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 46d98c6dfb99161a41982e2d2215d017b5520419..53f6b9e79d46d0bc606612908a121a8b33971e1c 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -576,7 +576,8 @@ bool Object::IsContext() {
             map == heap->with_context_map() ||
             map == heap->native_context_map() ||
             map == heap->block_context_map() ||
-            map == heap->module_context_map());
+            map == heap->module_context_map() ||
+            map == heap->global_context_map());
   }
   return false;
 }
@@ -589,13 +590,6 @@ bool Object::IsNativeContext() {
 }
 
 
-bool Object::IsModuleContext() {
-  return Object::IsHeapObject() &&
-      HeapObject::cast(this)->map() ==
-      HeapObject::cast(this)->GetHeap()->module_context_map();
-}
-
-
 bool Object::IsScopeInfo() {
   return Object::IsHeapObject() &&
       HeapObject::cast(this)->map() ==