Add <pre> to nesting tags

java/org/chromium/distiller/webdocument/WebTag.java

 package org.chromium.distiller.webdocument;
 
 import java.util.HashSet;
 import java.util.Set;
 
 /**
  * This class represents HTML tags that need to be preserved over
  * the distillation process.
  */
 public class WebTag extends WebElement {
     private String tagName;
     private TagType tagType;
 
     public enum TagType {
         START, END
     }
 
     private static Set<String> nestingTags;
     static {
         nestingTags = new HashSet<String>();
         nestingTags.add("UL");
         nestingTags.add("OL");
         nestingTags.add("LI");
         nestingTags.add("BLOCKQUOTE");
+        nestingTags.add("PRE");
     }
 
     public WebTag(String tagName, TagType tagType) {
         this.tagName = tagName;
         this.tagType = tagType;
     }
 
     public boolean isStartTag() {
         return tagType == TagType.START;
     }
 
     public String getTagName() {
         return tagName;
     }
 
     @Override
     public String generateOutput(boolean textOnly) {
         if (textOnly) {
             return "";
         }
         return "<" + (isStartTag() ? "" : "/") + tagName + ">";
     }
 
     public static boolean canBeNested(String tagName) {
         return nestingTags.contains(tagName);
     }
 }