Make kAsciiDataHintTag have correct semantics for all both 1 and 2 byte string types.

src/objects-inl.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 323 matching lines @@
     case kTwoByteStringTag:
       return true;
     default:  // Cons or sliced string.  Need to go deeper.
       return GetUnderlying()->IsTwoByteRepresentation();
   }
 }
 
 
 bool String::HasOnlyAsciiChars() {
   uint32_t type = map()->instance_type();
-  return (type & kStringEncodingMask) == kOneByteStringTag ||
-         (type & kAsciiDataHintMask) == kAsciiDataHintTag;
+  return (type & kAsciiDataHintMask) == kAsciiDataHintTag;
 }
 
 
 bool StringShape::IsCons() {
   return (type_ & kStringRepresentationMask) == kConsStringTag;
 }
 
 
 bool StringShape::IsSliced() {
   return (type_ & kStringRepresentationMask) == kSlicedStringTag;
@@ skipping 5205 matching lines @@
 #undef WRITE_UINT32_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_