Re-enable an UNREACHABLE in JSObject::GetHeaderSize()

src/objects-inl.h

 // 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.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 1961 matching lines @@
       return JSWeakMap::kSize;
     case JS_WEAK_SET_TYPE:
       return JSWeakSet::kSize;
     case JS_REGEXP_TYPE:
       return JSRegExp::kSize;
     case JS_CONTEXT_EXTENSION_OBJECT_TYPE:
       return JSObject::kHeaderSize;
     case JS_MESSAGE_OBJECT_TYPE:
       return JSMessageObject::kSize;
     default:
-      // TODO(jkummerow): Re-enable this. Blink currently hits this
-      // from its CustomElementConstructorBuilder.
-      // UNREACHABLE();
+      UNREACHABLE();
       return 0;
   }
 }
 
 
 int JSObject::GetInternalFieldCount() {
   DCHECK(1 << kPointerSizeLog2 == kPointerSize);
   // Make sure to adjust for the number of in-object properties. These
   // properties do contribute to the size, but are not internal fields.
   return ((Size() - GetHeaderSize()) >> kPointerSizeLog2) -
@@ skipping 5536 matching lines @@
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_