Remove the Document.charset setter (making it readonly)

Source/core/frame/UseCounter.h

 /*
  * Copyright (C) 2012 Google, Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 348 matching lines @@
         // The above items are available in M36 branch.
 
         ElementRequestPointerLock = 417,
         VTTCueRenderRtl = 418,
         PostMessageFromSecureToInsecure = 419,
         PostMessageFromInsecureToSecure = 420,
         DocumentExitPointerLock = 421,
         DocumentPointerLockElement = 422,
         PrefixedCursorZoomIn = 424,
         PrefixedCursorZoomOut = 425,
-        DocumentSetCharset = 427,
         DocumentDefaultCharset = 428,
         TextEncoderConstructor = 429,
         TextEncoderEncode = 430,
         TextDecoderConstructor = 431,
         TextDecoderDecode = 432,
         FocusInOutEvent = 433,
         MouseEventMovementX = 434,
         MouseEventMovementY = 435,
         DocumentFonts = 440,
         MixedContentFormsSubmitted = 441,
@@ skipping 409 matching lines @@
 
     bool hasRecordedMeasurement(Feature feature) const { return m_countBits.hasRecordedMeasurement(feature); }
 
     CountBits m_countBits;
     BitVector m_CSSFeatureBits;
 };
 
 } // namespace blink
 
 #endif // UseCounter_h