code: function( isReadOnly ) {
  			isReadOnly = ( isReadOnly == null ) || isReadOnly;
  
  			if ( this.readOnly != isReadOnly ) {
  				this.readOnly = isReadOnly;
  
  				// Block or release BACKSPACE key according to current read-only
  				// state to prevent browser's history navigation (#9761).
  				this.keystrokeHandler.blockedKeystrokes[ 8 ] = +isReadOnly;
  
  				this.editable().setReadOnly( isReadOnly );
  
  				// Fire the readOnly event so the editor features can update
  				// their state accordingly.
  				this.fire( 'readOnly' );
  			}
  		}
docs: Puts or restores the editor into read-only state. When in read-only,
  the user is not able to change the editor contents, but can still use
  some editor features. This function sets the {@link #property-readOnly}
  property of the editor, firing the {@link #event-readOnly} event.
  
  **Note:** the current editing area will be reloaded.
  
  @since 3.6
  @param {Boolean} [isReadOnly] Indicates that the editor must go
  read-only (`true`, default) or be restored and made editable (`false`).