code: function mergePre( preBlock ) {
  		var previousBlock;
  		if ( !( ( previousBlock = preBlock.getPrevious( nonWhitespaces ) ) && previousBlock.type == CKEDITOR.NODE_ELEMENT && previousBlock.is( 'pre' ) ) )
  			return;
  
  		// Merge the previous <pre> block contents into the current <pre>
  		// block.
  		//
  		// Another thing to be careful here is that currentBlock might contain
  		// a '\n' at the beginning, and previousBlock might contain a '\n'
  		// towards the end. These new lines are not normally displayed but they
  		// become visible after merging.
  		var mergedHtml = replace( previousBlock.getHtml(), /\n$/, '' ) + '\n\n' +
  			replace( preBlock.getHtml(), /^\n/, '' );
  
  		// Krugle: IE normalizes innerHTML from <pre>, breaking whitespaces.
  		if ( CKEDITOR.env.ie )
  			preBlock.$.outerHTML = '<pre>' + mergedHtml + '</pre>';
  		else
  			preBlock.setHtml( mergedHtml );
  
  		previousBlock.remove();
  	}
docs: Merge a <pre> block with a previous sibling if available.