[XML Viewer crash] Store the reference of pretty-print div as tree to be used during the processing

Source/core/xml/XMLViewer.js

 /*
  * Copyright (C) 2011 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.
  *
@@ skipping 12 matching lines @@
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 var nodeParentPairs = [];
 
 // Script entry point.
 
+var tree;
+
 function prepareWebKitXMLViewer(noStyleMessage)
 {
     var html = createHTMLElement('html');
     var head = createHTMLElement('head');
     html.appendChild(head);
     var style = createHTMLElement('style');
     style.id = 'xml-viewer-style';
     head.appendChild(style);
     var body = createHTMLElement('body');
     html.appendChild(body);
@@ skipping 10 matching lines @@
     document.appendChild(html);
 
     var header = createHTMLElement('div');
     body.appendChild(header);
     header.classList.add('header');
     var headerSpan = createHTMLElement('span');
     header.appendChild(headerSpan);
     headerSpan.textContent = noStyleMessage;
     header.appendChild(createHTMLElement('br'));
 
-    var tree = createHTMLElement('div');
+    tree = createHTMLElement('div');
     body.appendChild(tree);
     tree.classList.add('pretty-print');
-    tree.id = 'tree';
     window.onload = sourceXMLLoaded;
 }
 
 function sourceXMLLoaded()
 {
     var sourceXML = document.getElementById('webkit-xml-viewer-source-xml');
     if (!sourceXML)
         return; // Stop if some XML tree extension is already processing this document
-    var root = document.getElementById('tree');
 
     for (var child = sourceXML.firstChild; child; child = child.nextSibling)
-        nodeParentPairs.push({parentElement: root, node: child});
+        nodeParentPairs.push({parentElement: tree, node: child});
 
     for (var i = 0; i < nodeParentPairs.length; i++)
         processNode(nodeParentPairs[i].parentElement, nodeParentPairs[i].node);
 
     drawArrows();
     initButtons();
 
     if (typeof(onAfterWebkitXMLViewerLoaded) == 'function')
       onAfterWebkitXMLViewerLoaded();
 }
@@ skipping 334 matching lines @@
         expandButton.onmousedown = handleButtonMouseDown;
     }
 
 }
 
 function handleButtonMouseDown(e)
 {
    // To prevent selection on double click
    e.preventDefault();
 }